Scielo RSS <![CDATA[Salud mental]]> http://www.scielo.org.mx/rss.php?pid=0185-332520080003&lang=es vol. 31 num. 3 lang. es <![CDATA[SciELO Logo]]> http://www.scielo.org.mx/img/en/fbpelogp.gif http://www.scielo.org.mx <![CDATA[<b>Neglected priorities of mental health programmes</b>]]> http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S0185-33252008000300001&lng=es&nrm=iso&tlng=es <![CDATA[<b>Trastorno obsesivo compulsivo en niños y adolescentes: una actualización. </b><b>Primera parte</b>]]> http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S0185-33252008000300002&lng=es&nrm=iso&tlng=es The obsessive-compulsive disorder (OCD) is being reported now with increased prevalence in pediatric population than in the past, associated with the development of more specific assessment methods. This evolution has opened the possibility to characterize OCD presentation in children and adolescents. OCD in childhood is a chronic and distressing disorder that can lead to severe impairments in social, academic and family functioning. Currently, pediatric OCD criteria are the same than in adults. The presence of obsessive and compulsive symptoms are needed to establish the diagnosis but, because of the lower levels of cognitive awareness in children, they are less likely to consider their OCD symptoms as excessive or unreasonable. The DSM-IV does not require that symptoms be recognized as senseless or unrealistic for the diagnosis to be made in children. Overall, there are several clinical differences in the younger age groups that make this disorder a diagnostic and treatment challenge for clinicians. Epidemiologic studies have been conducted in adolescent population. These studies report a prevalence in the range of 2% to 4% with a slight predominance in males than females. In Mexico, there are no studies in this population to confirm these rates. Frequently children, more than adolescents and adults, may present compulsive behavior without obsessions, which are related to immature cognitive development. The obsessive-compulsive symptoms have differences between age groups (children, adolescents and adults). Children may be somewhat more likely to engage in compulsive reassurance- seeking and involve their parents in their rituals. The most common obsessions in childhood are related to contamination and germs, followed by fears to harm others. The most common compulsions are washing, repeating and checking. Adolescents present more frequently religious and sexual contents in their obsessions, and similar about aggression as children. Related to compulsions, children and adolescents develop hoarding more frequent than adults. Several studies suggest a mean age of childhood OCD from 6 to 11 years of age, but there are two peaks of more frequent cases presentation: in early childhood and early adolescence. Regarding the OCD early-onset, course studies have reported chronicity in most subjects, 50% of them meeting full OCD criteria seven years later. Meta-analytic studies about predictors and persistence of pediatric OCD diagnoses show persistence in 41% of the sample with full OCD and 60% full or sub-threshold OCD. Early beginning of OCD increase duration of illness and is a predicted of major persistence. Comorbid psychiatric illnesses and poor initial treatment response were poor prognostic factors. Regarding symptoms during illness course, the pattern and type frequently shift over time, although the number of symptoms typically remains constant. Pediatric OCD has evoked distinct classifications related to the familiar presentation form and comorbidity, especially with tics disorders. Studies have reported that children with tics disorders show several differences in their reported symptom types when compared with the group with no history of tics, for example, they are more likely to endorse repetition of routine behaviors unrelated to harm avoidance. Contamination and washing rituals are more common in the OCD child without tics. Findings are consistent with several studies in clinical assessed adult samples which have shown that the tic-related OCD can be distinguished as a subtype of OCD. These adults are more likely to report obsessions involving a need of symmetry and compulsions involving touching, starting and counting. There are also evidence that the tic-related OCD may be lees likely to monotherapy with a selective serotonin reuptake inhibitor. Another way to understand this disorder is subtyping symptoms using factorial analysis. Several authors have proposed at least four subtypes or factors (washers, hoarders, checkers and sexual/religions symptoms). Some studies with children and adolescents have shown limitations to conduct a factorial analysis, although some others with better methods have showed similarity between OCD symptoms dimensions structure in children and adults. The etiology of OCD is not clear, but the evidence in familiarity, segregation analysis and twins studies have established the role of genetics in the cause factors and is considered as a complex genetic disorder. Twin studies find a high concordance rate for monozygotic twins (53-87%) and dizygotic twins (22-47%). The prevalence of OCD is higher among first degree relatives of affected subjects, early-onset OCD has a higher rate of first degree relatives with TOC. Association studies with candidate genes have been done in early-onset OCD but significant results have not been replicated.<hr/>El trastorno obsesivo compulsivo se ha reportado en los últimos tiempos con mayor prevalencia en la edad pediátrica que lo reportado anteriormente, esto se debe probablemente a una mejor caracterización de su presentación en niños y adolescentes y al desarrollo de mejores métodos de evaluación. Los criterios diagnósticos son los mismos para niños, adolescentes y adultos. Debido a su bajo nivel de conciencia, los niños pueden no considerar sus obsesiones como exageradas o ilógicas por lo que el DSM-IV no incluye este criterio en este grupo de edad. Aunque hay muchas similitudes sintomáticas a distintas edades, también hay importantes diferencias que convierten este padecimiento en un reto diagnóstico y de tratamiento en el TOC de inicio temprano. La prevalencia del TOC pediátrico se ubica en un rango de 2% a 4%, con una predominancia de los hombres en relación a las mujeres. En México aún no se cuenta con estudios que confirmen estas cifras en esta forma de presentación pediátrica. Frecuentemente los niños, más que los adolescentes y los adultos, pueden presentar conductas compulsivas, sin un componente obsesivo, lo cual probablemente se asocie al desarrollo cognitivo. Los síntomas obsesivos y compulsivos presentan diferencias en el contenido de acuerdo al grupo etario. Las obsesiones más comunes en el TOC de inicio temprano son las relacionadas a la contaminación y gérmenes con compulsiones relacionadas a lavado y revisión. Otras obsesiones frecuentes son el temor a dañar a otros. Se ha identificado que los adolescentes presentan con mayor frecuencia obsesiones sexuales o religiosas y, junto con los niños, más obsesiones agresivas y compulsiones de atesoramiento que los adultos. Por sus características el TOC de inicio en la infancia ha dado pauta a diversas clasificaciones, como son la presencia comórbida de tics y la agregación familiar con más de un integrante con el padecimiento. Algunos estudios han reportado diferencias entre los niños que padecen TOC con tics versus aquellos sin tics, como es la mayor frecuencia de rituales de repetición sin contexto de evitación al daño y menor frecuencia de síntomas relacionados con contaminación/lavado. Otra forma de clasificación que en la actualidad ha permitido la subdivisión del TOC en subtipos se ha apoyado en el análisis factorial, donde se han identificado subtipos en adultos y recientemente en niños y adolescentes con consistencia entre autores. Los subtipos propuestos son: lavado/contaminación, simetría/ orden, obsesiones sexuales/religiosas y atesoramiento. Respecto de las hipótesis etiológicas, las evidencias de agregación familiar y los estudios en gemelos han esclarecido el importante papel genético de este trastorno. Otras teorías biológicas no genéticas para el TOC que se han considerado son las lesiones cerebrales focales y secuelas inmunes generadas por infecciones con el estreptrococo beta-hemolítico del grupo A que podrían explicar alguna proporción de los individuos con TOC. Diversas líneas de investigación han evidenciado que la neuropatología del TOC se encuentra en el circuito cortico-estriado-tálamo-cortical, donde están implicadas la disfunción de la dopamina, la serotonina, el glutamato y el GABA. Particularmente existe evidencia sobre la serotonina, dada la amplia utilización y probada efectividad de los inhibidores selectivos de la recaptura de serotonina (ISRS) en el tratamiento del TOC. Los estudios electrofisiológicos y con potenciales relacionados con eventos (PREs) han sido limitados en adultos y no hay reportes en población pediátrica. Por medio de estudios de neuroimagen como la tomografía axial computarizada (TAC), se ha reportado: disminución de volumen bilateral en el núcleo caudado y cambios estructurales en los ganglios basales ante sintomatología obsesivo-compulsiva durante la adolescencia. La tomografía por emisión de positrones (TEP) en adultos ha sugerido un incremento en el metabolismo del giro orbital y la cabeza del núcleo caudado, mientras que en sujetos con una edad de aparición en la adolescencia se ha reportado un incremento en el metabolismo en regiones orbito-frontal izquierda, sensorio-motor derecha, giro del cíngulo anterior y prefrontal bilateral. <![CDATA[<b>Efecto de una intervención antitabaco en estudiantes de enseñanza media superior en Guadalajara, México</b>]]> http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S0185-33252008000300003&lng=es&nrm=iso&tlng=es Introduction Recent data, both domestic and from the world over, have shown that the epidemiologic impact of tobacco consumption has a higher increase rate among adolescent population, particularly women, than in the general population. This has highlighted the need to implement preventive intervention programs focused on young people. The school environment seems to be the most adequate space to achieve such a goal. Most school intervention reports aimed at reducing tobacco consumption among students have been carried out in the United States and have both had a positive effect and proven to be cost-effective. In Mexico, there is only one antecedent of a successful prevention program conducted in an elementary school. Results from this suggest that behavioural abilities acquisition reduces the prevalence of tobacco experimentation and promotes cessation among those already using it. Given the lack of educational interventions and the fact that tobacco consumption tends to increase among Mexican high school students, we conducted this study aiming to implement an educational intervention on tobacco consumption among adolescent high school students from the Universidad de Guadalajara, Mexico. Later on we proceeded to evaluate its effect. Material and methods Based on a diagnostic and a literature review from successful anti-tobacco consumption programs, we devised a campaign called <<Stop burning yourself out>>. This lasted for half a school year and included parents, teachers and non-smoking peers. Parents participated in five sessions aimed at promoting abstinence from tobacco consumption at home. Forty-two teachers, trained as campaign mediators, participated. A manual describing the contents from each session was elaborated for quality control purposes. Students themselves participated in four monthly sessions, were given anti-tobacco messages, watched anti-tobacco educational documentaries -under the supervision and discussion of a professor-, and exchanged cigarettes for chewing gum with non-smoking peers. In addition, a Tobacco Clinic was established, a mouth-teeth exam was carried out, and an anti-tobacco poster was displayed at the school. The poster message was changed each month. School measures regarding the ban on cigarettes sale on the school premises were likewise reinforced. Right before starting the campaign and immediately after finishing it, tobacco consumption rates, the type of consumption, the likelihood of using tobacco in the near future and the level of understanding as to the harmful effects on health of tobacco consumption were all evaluated using validated and standardized surveys. All measurements were carried out with an electronic questionnaire. The intervention effect evaluation was carried out with two independent samples: a base sample and a final sample before the campaign conclusion. Calculation of the sample size required for both surveys was based on data from a diagnostic study conducted at the same school. Participants were randomly selected. The project was approved by an Ethics and Research Committee from the Instituto Mexicano del Seguro Social (National Social Security Institute) and all the students participated in the educational intervention. Results Whereas 621 adolescents participated in the base evaluation, a total of 524 of them took part in the final evaluation. Parental attendance at the various sessions changed from 90% to 20%. A total of 2675 mouth-teeth exams were carried out. At these, tooth cavities decay, lack of dental hygiene and gengivitis were detected. In turn, this resulted in suggestions to attend regular health care services for treatment. At the Tobacco Clinic, a group of 20 family parents was formed for treatment. The once-in-a-lifetime, in the last 12 months, and in the last previous month tobacco consumption prevalence accounted to 43.6%, 23.0%, and 24.3%, respectively. Experimental versus regular tobacco consumption were 34.9% and 7.2%. Nonsmoking population was 57.8%. In the same base evaluation, 9.7% of the students considered it was very likely they would smoke in the future, 46.9% considered it barely likely, and 43.5% considered they would never smoke in the future. The positive effect of the campaign was reflected in the type of tobacco consumption as there was a reduction in the rate of experimental smokers, as well as an increase in the number of non-smokers in the final evaluation compared to the base one. The rate of regular smokers did not change from one evaluation to the other. The once-in-a-lifetime, in the last twelve months, and in the last month frequency of consumption, together with the likelihood of smoking in the near future, showed no changes in the final evaluation compared to the base one. In the base evaluation, a high level of understanding about the harmful effects of tobacco on the pulmonary system and a moderate level of understanding about the harmful effects of tobacco on the heart and the female reproductive system, as well as on the stomach and liver, were observed, while there was a low level of understanding about the harmful effects of tobacco on the rest of the organic systems. In the final evaluation, it was observed that the understanding level of organic systems about which it was moderate or high remained the same. In addition, a significant increase of the understanding about the harmful effects of tobacco on the ocular system and the urinary tracts was observed. The level of understanding about the harmful effects of tobacco on the rest of the organic system remained also the same.<hr/>Introducción La mayor parte de los reportes de intervenciones escolares para reducir el consumo de tabaco en estudiantes han sido realizados en Estados Unidos y han mostrado un impacto positivo además de que son costo/efectivas. En México solamente existe el antecedente de un estudio exitoso de un programa de prevención de tabaco realizado en primaria, cuyos resultados sugieren que el desarrollo de habilidades conductuales reduce la prevalencia de la experimentación de tabaco y promueve el cese en quienes ya lo consumen. Ante la falta de intervenciones educativas y la tendencia hacia el aumento del consumo de tabaco en adolescentes escolares de educación media superior en México, realizamos el presente estudio con el objetivo de implementar y evaluar el efecto de una intervención educativa sobre el consumo de tabaco en adolescentes de una preparatoria de la Universidad de Guadalajara, en la ciudad de Guadalajara, capital del Estado de Jalisco, México. Material y métodos Basándose en un diagnóstico previo se diseño una campaña antitabaco, dirigida a adolescentes fumadores, con una duración de un semestre escolar, que incluyó la participación de padres de familia, maestros y pares no fumadores. Antes del inicio e inmediatamente después de finalizar la campaña se evaluaron, mediante dos muestras independientes por medio de encuestas validadas y estandarizadas, la frecuencia de consumo de tabaco, el tipo de consumo, la probabilidad de consumir tabaco en un futuro cercano y el nivel de conocimientos sobre los efectos nocivos para la salud que produce su consumo. Resultados El efecto positivo de la campaña se apreció en el tipo de consumo de tabaco puesto que hubo una reducción de la proporción de fumadores leves así como un incremento del número de no fumadores en la evaluación final con respecto a la basal; la proporción de fumadores moderados no se modificó en ambas evaluaciones. La frecuencia de consumo una vez en la vida, en los últimos doce meses, en el último mes, así como la probabilidad de fumar en un futuro cercano no mostró modificaciones en la evaluación final con respecto a la basal. Discusión La intervención educativa antitabaco tuvo efectos positivos sobre el tipo de consumo de tabaco en los adolescentes de la escuela sede, que se evidenciaron en la disminución de la proporción de fumadores leves, en el incremento de no fumadores y en el incremento del nivel de conocimientos sobre los efectos nocivos del consumo de tabaco sobre la salud. Creemos que la explicación se vinculó a tres aspectos: 1) por haber diseñado la intervención a partir de un diagnóstico escolar, 2) por haber tomado en cuenta las diferentes influencias sociales al incorporar la participación de maestros, pares no fumadores y padres de familia, 3) por la inclusión de sugerencias de programas exitosos en la modificación actitudinal. La intervención implementada resultó ineficaz para fumadores moderados, por lo que se tendría mayor efecto preventivo si se aplicaran en estudiantes de educación básica y media básica, en quienes el consumo de tabaco aún tiene un impacto inicial. A partir de la falta de interés mostrado por los padres, hipotetizamos que en ellos parece prevalecer una actitud permisiva en el consumo de tabaco de sus hijos y parecen subestimar la posibilidad de influir en su consumo. Se considera que los padres representan un contexto preventivo importante en el tabaquismo del adolescente. A partir de esto se plantean hipótesis y nuevas preguntas para ser investigadas. El estudio presenta limitaciones al no haberse incluido un grupo control y por haber limitado la evaluación de la intervención al periodo inmediato posterior. Sin embargo, pensamos que a pesar de estas limitaciones la intervención educativa antitabaco es efectiva para la reducción del consumo de tabaco experimental y en el incremento del nivel de conocimientos de los efectos deletéreos sobre la salud. <![CDATA[<b>Evaluación de factores asociados a la ansiedad social y a otras psicopatologías en adolescentes</b>]]> http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S0185-33252008000300004&lng=es&nrm=iso&tlng=es Introduction The study of factors associated with anxiety and social phobia is a subject of recent interest in mental health. Specifically, shyness in children seems to act as an early expression of social phobia that may later consolidate into a clinical entity. The presence of certain psychopathologies and particular styles of child rearing in parents, are perceived by their children, are associated with the emergence of social phobia in adolescence. On the other hand, social anxiety disorder during adolescence or early adulthood may predict subsequent depressive disorders. The presence of both disorders (anxiety and social phobia) during adolescence increases the probability of suffering from them recurrently in early adulthood. Family structure and cohesion as well as stressful life events have been found to be associated with mood disorders during the childhood-youth period. However, studies conducted with young subjects are scarce, even though understanding the factors associated to different psychopathologies in the youth has proven of great value in clinical practice and epidemiology. For this reason, we attempt to evaluate, in a sample of three groups of adolescents (social anxiety, other psychopathologies and without psychopathologies) the possible demographical factors, competences and clinical indexes that could be associated with the different conditions under consideration. Methodology A sample of 1012 adolescents (582 women and 430 men) with an average age of 15.80 years (SD = 1.48) fulfilled a series of tests to assess demographical variables, psychosocial competences and clinical indexes. Results The difference between the average scores in the Escala de Ansiedad en Interacción Social -SIAS- was significant for the variables sex and the school year. Sex and couple relationships significantly affect the probability of manifesting social anxiety and other psychopathologies, respectively. Some competences significantly affect the probability of social anxiety, whereas others affect the probability of developing other psychopathologies. The majority of the 46 clinical indexes assessed demonstrate a significant effect on the probability of developing both conditions. Discussion and conclusions The results indicate that, in line with previous studies, the average score of women in the SIAS is slightly higher than in men. The average score in the SIAS of the young people from formative cycles was slightly higher than in the subjects from the obligatory secondary education and high schools. Very few studies have informed on the differences in social anxiety associated with the educational level. Women presented significantly higher probability of suffering from social anxiety than men. Unexpectedly, adolescents who maintained couple relationships also showed significantly higher probabilities than the rest of suffering from other psychopathologies. Some psychosocial competences, especially those related to the situations of social interactions, have a significant effect on the probability of developing social anxiety, whereas others (social and behavioural) influence other psychopathologies. In general and to a large extent, the findings are coherent and explainable, although some of them are contradictory. This could be caused by the difficulty to evaluate the complex construct of psychosocial competences. The majority of the evaluated clinical indexes showed a significant effect on the probability of developing of social anxiety and other psychopathologies. This effect is more evident in the group of young people with other psychopathologies than in the group of adolescents with social anxiety. Previous studies have found similar results, especially in the indexes referring to the general measures of anxiety and depression, specific measures of anxiety and avoidance of social situations and personality.<hr/>Introducción El estudio de factores asociados a la ansiedad y fobia social constituye un tema de reciente interés. Concretamente, la timidez infantil parece actuar como una expresión temprana de la fobia social que más tarde se puede consolidar como cuadro clínico. La percepción de los hijos sobre la presencia de ciertas psicopatologías y de determinados estilos de crianza de los padres se asocia a la aparición de la fobia social en la adolescencia. El trastorno de ansiedad social durante la adolescencia o la adultez temprana puede predecir trastornos depresivos subsecuentes. La presencia de ambos trastornos (ansiedad y fobia social) durante la adolescencia incrementaría la probabilidad de padecerlos de manera recurrente a lo largo de la adultez temprana. La estructura y la cohesión familiar, así como los sucesos estresantes de la vida, se han asociado con trastornos afectivos en la etapa infanto-juvenil. En la actualidad, los estudios realizados en estas edades son escasos, aun cuando el entendimiento de los factores asociados a distintas psicopatologías en la edad temprana reviste importancia clínica y epidemiológica. Por ello, pretendemos evaluar en una muestra de adolescentes formada por tres grupos (ansiedad social, otras psicopatologías y sin psicopatologías) los posibles factores demográficos, de competencias e índices clínicos que pueden estar asociados a las diferentes condiciones estudiadas. Metodología Una muestra de 1012 adolescentes (582 mujeres y 430 hombres) con una edad media de 15.80 años (DT = 1.48) completó en su medio escolar una serie de pruebas que evalúan variables demográficas, competencias psicosociales e índices clínicos. Resultados La diferencia de medias en las puntuaciones de la Escala de Ansiedad en Interacción Social -SIAS- fue significativa para las variables sexo y curso escolar. El sexo y la relación de pareja ejercieron un efecto significativo en la probabilidad de manifestar ansiedad social y otras psicopatologías, respectivamente. Algunas competencias mostraron un efecto significativo en la probabilidad de presentar ansiedad social, mientras que otras lo hicieron en la probabilidad de desarrollar otras psicopatologías. La mayoría de los 46 índices clínicos evaluados mostró un efecto significativo en la probabilidad de sufrir ambas condiciones. Discusión y conclusiones Los resultados indican que la puntuación media de las mujeres en la SIAS superó ligeramente a la de los hombres, lo que coincide con estudios previos. La puntuación media en la SIAS de los jóvenes que formaron los ciclos formativos fue ligeramente superior a la de los procedentes de educación secundaria obligatoria y de bachillerato. Hay pocos estudios que informen de diferencias en la ansiedad social asociadas al nivel de estudios. Las mujeres presentaron una probabilidad significativamente mayor que los hombres de sufrir ansiedad social. Los adolescentes que mantenían relaciones de pareja también mostraron significativamente más posibilidades que el resto de presentar otras psicopatologías, el cual es un resultado inesperado. Algunas competencias psicosociales, especialmente las que se relacionan con las situaciones de interacción social, han mostrado un efecto significativo en la probabilidad de sufrir ansiedad social, mientras que otras (sociales y de actuación) lo han hecho en la probabilidad de desarrollar otras psicopatologías. En general, gran parte de estos hallazgos tienen coherencia y explicación, aunque algunos son contradictorios, lo que puede deberse a la dificultad de evaluar el constructo de competencias psicosociales por su complejidad. Por último, la mayoría de los índices clínicos evaluados presentó un efecto significativo en la probabilidad de desarrollar ansiedad social y otras psicopatologías. Este último efecto fue más notorio en el grupo de jóvenes con otras psicopatologías que en el grupo de adolescentes con ansiedad social. Diversos estudios encuentran resultados parecidos a los hallados en éste, especialmente en los índices referentes a medidas generales de ansiedad o depresión, específicas de ansiedad y evitación en situaciones sociales, y de personalidad. <![CDATA[<b>Modelo psicoeducativo para la prevención del suicidio en jóvenes</b>]]> http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S0185-33252008000300005&lng=es&nrm=iso&tlng=es Suicide occurrence is ever more often amongst 15-24-year-old youngsters, and it ranks as the second or third cause of death in some countries. Likewise, suicide attempts are more frequent amongst teenagers than amongst any other age group. Several studies agree that the portion of population with the highest suicide risk is that ranging from ages 15 to 24 and that Mexico is one of the countries wherein this trend, and suicide in general, is more rapidly increasing. On the other hand, almost 5% of all the country's suicides take place in the State of Guanajuato. The process of suicide is a complex and dynamic one that goes through a series of stages before culminating in the life-ending act. These phases, from merely picturing the idea to brandishing it as a verbal threat, planning and executing it, may very well be identified in advance, hence allowing for adequate intervention. Therefore, understanding suicide dynamics and identifying risk factors reduce the likelihood of suicide in specific populations: this is the core of suicide prevention. Such prevention programs take place within the every day environment of the people to whom they are targeted and their efficiency increase as the acknowledgement of both their needs and resources is more precise. It is because of this, and as a response to the lack of information pertaining suicide prevention programs in Mexico, that this report is presented. It stems from a preventive experience amongst high school youths in the State of Guanajuato. The aim of the aforementioned preventive workshop was to awaken risk prevention amongst high school students through a psycho-educative strategy. The workshop, called <<Saving Lives>>, inspired in the <<Gatekeeper>> model and based on previous studies of that same population, consisted of ten hours spliced in five two-hour sessions throughout which scientific information on suicide was presented, suicide-related myths analyzed, attendants were trained for detecting people at stake, and intervention, channeling and self-care suggestions were made. Suicide awareness was assessed both prior and upon workshop ending; furthermore, the workshop itself was evaluated through a questionnaire. Trained psychology students cursing the tenth semester were appointed coordinators and high school students of both sexes attended the workshop. The invitation was open to the general public and those who completed all five stages were certified <<Informed Guardians>>. The workshop was carried out in eight of the ten high schools administered by the Universidad de Guanajuato in the state. Sixty-nine students attended and completed all five set sessions. The average age of attendants was 16.1 years old; standard deviation was 1.3 years; 69% of them were female. Out of 22 possible points included in the suicide knowledge evaluation questionnaire, the average result on first answering was 12.59 correct answers, which rose to 15.97 upon completing the workshop. The range of grades was increased one point for both the minimum and the maximum values and standard deviation was reduced from 2.62 to 2.49. The increase in suicide knowledge was then proved through a <<T>> test for two dependent samples since it showed the significance of the result increase (p<0.001). The benefits of the workshop were tested through attendants' comments and coordinators reports analyses. Tearing down of suicide myths such as the confusion between the embracing of suicide ideas and their actual fulfillment, the consideration of suicide as a sign of either bravery or mental illness, the notion that talking about suicide with someone who has expressed his wish for committing suicide is tactless or that a suicidal does not show any warning signals were outstanding elements. The workshop evaluation questionnaire, objective fulfillment, workshop methodology, time management and topic selection were all praised by the attendants. The third workshop evaluation instrument involved the coordinators' reports, thus corroborating the workshop reach and gaining further information: six of the attendants knew someone who had tried suicide; seven more had embraced suicidal ideas, of whom five actually tried them out actively. <<Saving Lives>> left amongst its conclusions the fact that 12 out of 69 attendants acknowledged having either embraced or tried suicide previously. This could have proved motivation enough so as to become <<Informed Guardians>> and pin-points the importance or teenage prevention, for not only are they the group with the highest risk but also because they are the first to know of changes and/or suicide risk within their circle of friends. Besides, when trained as suicide prevention agents, they may spread the word and adequate information not only in school-based environments but wherever they happen to interact, be it at home or recreational centers, amongst many others. Another benefit that stems from the workshop is an even more accurate definition of suicide concepts. Several suicide myths were clarified. The fact that the workshop coordinators were students was regarded as positive by both attendants and the coordinators themselves. In spite of the appalling increase in mortality figures due to suicide, there are virtually no suicide prevention programs in Mexico, and the scarce ones are utterly limited. The proposed workshop proved a means of effective objective reach since not only does it provide information pertaining specific suicide facts but also focuses on the needs and helping possibilities embodied by the <<Informed Guardians.>> Moreover, thanks to having been designed based on previous studies of the same population, it is so flexible a project that it can be adapted for further use in elementary schools. Such an extensive and urgent task as suicide prevention should summon the combined effort of all social spheres. The established misconception that suicide care is a responsibility constrained to certain institutions, limits the individual responsibility so much as the society's, as well as prevention itself. An effective dispel of such conception amongst young attendants was another achievement of the workshop. The challenge now is to reach cooperation agreements with all social participants who have a word in it so as to stop and revert the current increasing trend in suicide.<hr/>El fenómeno del suicidio impacta cada vez más en la población joven de entre 15 y 24 años de edad y en algunos países es la segunda o tercera causa de muerte en ese sector. Diversos estudios coinciden en señalar que ése es el segmento poblacional con mayor riesgo suicida y que México es uno de los países en los que esta tendencia se incrementa más rápido. Por otro lado, en el Estado de Guanajuato tienen lugar casi 5% de los suicidios ocurridos en todo el país. El proceso dinámico y complejo del suicidio pasa por varias etapas antes de culminar en el acto que le quita la vida a la persona. Sus fases previas pueden ser identificadas oportunamente para dar pie a la intervención adecuada. De este modo, el conocimiento específico de la dinámica del suicidio sumado al reconocimiento de los factores de riesgo, reduce la probabilidad de su aparición, es decir, lo previene. Por este motivo, y como respuesta ante la falta de reportes sobre programas de prevención del suicidio en México, se presenta esta experiencia preventiva con jóvenes del nivel de educación medio superior del Estado de Guanajuato. El objetivo del taller fue incidir en la prevención de riesgo suicida en estudiantes del nivel medio superior por medio de una estrategia psicoeducativa. El taller <<Salvando Vidas>>, fundamentado en estudios previos en esa misma población, constó con una duración de diez horas divididas en cinco sesiones. Se evaluaron los conocimientos relativos al suicidio antes y al finalizar el taller, además de que los asistentes evaluaron al propio taller mediante un cuestionario. El taller fue llevado a cabo en ocho de las diez preparatorias con que cuenta la Universidad de Guanajuato en el Estado. Participaron en total 69 estudiantes (69% mujeres). El promedio de edad de los asistentes fue de 16.1 años con desviación estándar de 1.3 años. La puntuación promedio obtenida en el cuestionario de evaluación de conocimientos sobre suicidio aumentó de 12.59 respuestas correctas al inicio, a 15.97 al finalizar el taller. El rango de calificaciones se incrementó en un punto y la desviación estándar se redujo. La mejora en los conocimientos evaluados se constató mediante una prueba T para dos muestras dependientes (p<0.001). Otro de los beneficios del taller fue que favoreció el derrocamiento de mitos en torno al suicidio. En el cuestionario de evaluación del taller, el cumplimiento de los objetivos y la metodología empleada fueron calificados positivamente. Además, seis de los participantes conocían a alguien que ha intentado quitarse la vida, siete más reconocieron haber tenido ideación suicida y cinco de ellos lo habían intentado. Se concluye que es un imperativo intervenir preventivamente con los adolescentes ya que no sólo son el grupo de mayor riesgo suicida, sino porque además son los primeros en enterarse de cualquier riesgo suicida en su grupo de amigos y además al estar capacitados para prevenirlo pueden ser multiplicadores de una mayor conciencia y de información adecuada en otros ámbitos en donde conviven. El taller demostró ser una forma eficaz de prevenir el suicidio porque no sólo aporta información sobre aspectos específicos, sino que también contempla las necesidades y posibilidades de ayudar del <<Guardián informado>>. Además, el hecho de estar diseñado sobre la base de estudios previos con esa misma población, le hace de tal modo flexible que es posible adaptarlo para su aplicación en centros escolares de educación básica; el reto a futuro es lograr la colaboración entre todos los actores sociales que tienen algo que aportar para detener el alza del suicidio. <![CDATA[<b>Relación entre la emoción expresada por el familiar responsable y la conducta sintomática de pacientes con esquizofrenia, incluido el funcionamiento social</b>]]> http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S0185-33252008000300006&lng=es&nrm=iso&tlng=es In the 1950's, several authors carried out a series of studies focusing on the course of schizophrenia rather than its etiology. They found a link between the living conditions to which patients returned after being discharged from the hospital, and their risk of relapse. A higher risk was observed in those patients that returned to their conjugal or parental home, compared to those who returned to other living conditions. This line of work that explored stressful family mechanisms coined a term known as expressed emotion (EE) -high and low- in the family, which refers to the evaluation of the quantity and quality of attitudes and feelings such as criticism, hostility and over-involvement of a family member towards the person diagnosed with schizophrenia. These attitudes among family members have been associated with the presence of relapse in patients two years after being discharged from the hospital when family members and the patient live in the same household and are in contact 35 hours or more per week. It has been proved that these attitudes exert an influence, either increasing or decreasing the exacerbation of symptoms and, in some cases, leading to the patient's rehospitalization. Higher rates of relapse (92%) have been found in patients that spend over 35 hours a week with the relative in charge (RIC) and were not taking antipsychotic medication. It has also been found that when a RIC with high EE is in close contact with the patient, the latter is at risk of experiencing a symptom exacerbation that increases two to four times the probability of relapse. The most typical emotional expressions are critical comments, hostility, and excessive affective involvement. Criticism and over-involvement are usually perceived as stressful. Criticism implies intolerance and disapproval, whereas over-involvement suggests intrusiveness and control, and includes high levels of anxiety in the patient. Some positive aspects are also found, like the demonstration of warm feelings. a) Criticism. Includes comments and statements which due to the way that are expressed by the RIC represent unfavorable comments about the behavior or personality of the individual being referred to. In other words, it shows aversion or disapproval of a person's behavior or characteristics. b)Over-involvement. More commonly found in parents than in other relatives, it includes over-protection or consent, self-sacrifice and emotional distress. The patient is regarded as less competent and more vulnerable. c) Hostility. Generally occurs when there is criticism, which is why it is of little value as an independent predictor. Hostility occurs when the patient is attacked for what he is, rather than for what he does. The main objective of this article is to show the relationship between the level of expressed emotion (EE) (high or low) of the relative in charge with symptomatic behavior (SB) and social functioning (SF) of the patient with schizophrenia. It also includes a proposal of a conceptual model to evaluate the predictive factors of high EE. A transversal non-probabilistic study of 33 relatives of patients with schizophrenia was carried out. The relatives were contacted through the Schizophrenia Clinic in the outpatient unit at the hospital of The National Institute of Psychiatry Ramón de la Fuente in Mexico City. The instruments used were: 1. The Social Behavior Assessment Schedule (SBAS) and 2. The Questionaire for Measuring the Level of Expressed Emotion (Cuestionario-encuesta, evaluación del nivel de EE [CEEE]). The results indicated that 14 (42.4%) of the interviewed relatives had high EE and 19 (57.6%) had low EE. The main characteristics associated with high EE in RIC were: living in the same household with the patient's mean age of 54.8 years, having less than 12 years of education, being employed and not having a spouse. The most frequent expressed emotions were criticism, hostility and over-involvement. In patients, the main characteristics were: being male, young, with a mean age of 29.2 years, single and without employment alternatives, with two or more relapses and with a diagnosis of schizophrenia for five or more years. The presence of symptoms in the patient's according to relatives with low EE was 31.6% as opposed to 74.1% reported by RIC with high EE. Relatives with high EE mentioned greater personal neglect, irritability, violent behavior and isolation on the part of the patient, whereas relatives with low EE reported more fears, forgetfulness, dependence and strange ideas as problematic behaviors in the patients. The differences found between relatives with high and low EE regarding the patients' functioning were clearly demonstrated. Relatives with low EE reported better functioning in patients' performance of chores, demonstration of affect, involvement in leisure activities and better communication skills. Relatives with low EE reported that the persistence of the symptoms in their patients was 31.6%, whereas for those with high EE it was 71.4%. A logistic regression was used to identify the best predictors of EE, where the dependent variable was the total EE score, and the predictors were the continuous variables for social functioning and symptomatic behavior. A significant association was found between the two variables. Poor social functioning, symptomatic instability in the patient and being the patient's sibling explained 46% of the variance in RIC with high EE. The predictors had high levels of statistical significance. The model revealed the independent contribution of each variable and its interaction with the others. The level of family EE can be considered as the best predictor of relapse in patients with schizophrenia. Thus, EE acquires a special relevance: when high EE causes relapse, the reduction of the level of EE will lead to a decrease in relapse rates. Although the traditional means of measuring EE through the CFI has been found to be highly effective, it takes a long time to apply and classify the answers of the instrument. Another alternative is the CEEE that has been used in this study, since it has been used in other clinical trials due to the brief time required for training, application and classification of the data.<hr/>La línea de estudios que contempla los mecanismos familiares estresantes utiliza un concepto denominado Emoción Expresada (EE) en el ambiente familiar, que se refiere a la evaluación de la cantidad y calidad de las actitudes y sentimientos relacionados con la crítica, hostilidad y sobreinvolucramiento que uno de los familiares expresa acerca de uno o varios miembros de la familia diagnosticado con esquizofrenia. Estas actitudes de los familiares se han asociado con la presencia de recaídas en los pacientes a los dos años de haber sido dados de alta, especialmente cuando los miembros de la familia y el paciente conviven en el mismo espacio y pueden tener contacto por lo menos 35 horas o más semanales. Las expresiones emocionales más características comprenden: comentarios críticos, hostilidad, exceso de involucramiento afectivo y aspectos positivos como la calidez, los cuales son percibidos en general como estresantes. La crítica implica intolerancia y desaprobación, el sobreinvolucramiento sugiere intrusividad y control, que incluyen niveles altos de ansiedad en el paciente y que se describen de la siguiente manera: a) La crítica. Originalmente fue definida como aquellos comentarios o aseveraciones los cuales, por la manera en que son expresados, constituyen comentarios desfavorables sobre la conducta o personalidad del individuo a quién se refiere. Es decir, muestran aversión o desaprobación de la conducta o las características de una persona. b) El sobreinvolucramiento o sobreprotección. Se presenta más comúnmente en los padres que en algún otro familiar; está compuesta por aspectos de sobreprotección o consentimiento, autosacrificio y malestar emocional, es similar al trato que generalmente se le da a un niño sobreprotegido, con niveles inapropiados de preocupación por parte del familiar. El paciente es visto como menos competente que antes y más vulnerable. c) La hostilidad. Se presenta cuando existe crítica, por lo que tiene poco valor como predictor independiente. Se considera que está presente cuando el paciente es atacado por lo que es, más que por lo que hace, lo que refleja una dificultad para tolerar y algunas veces para comprender la situación del familiar enfermo. El propósito de este trabajo consiste en mostrar la relación entre el tipo de Emoción Expresada (EE) (tanto alta como baja) por el familiar responsable (FR), y la Conducta Sintomática (CS), así como con el Funcionamiento Social (FS) del paciente con esquizofrenia. Se plantea también un modelo conceptual para evaluar los factores predictores de la EE alta. Se utilizó un diseño transversal de una muestra no probabilística y de tipo circunstancial, la selección fue de manera secuencial, los sujetos de estudio fueron 33 familiares responsables de pacientes con esquizofrenia, que asistían a la consulta externa de la Clínica de Esquizofrenia del Instituto Nacional de Psiquiatría Ramón de la Fuente, en la Ciudad de México. Los instrumentos empleados fueron: 1. Cédula de evaluación de la conducta del paciente (SBAS) y 2. Cuestionario-encuesta, evaluación del nivel de Emoción Expresada (CEEE). Los resultados indicaron que los familiares con EE alta observaron un mayor descuido personal, irritabilidad, violencia y aislamiento por parte del paciente, en tanto que los familiares con EE baja reportaron más miedos o temores, olvidos, dependencia e ideas extrañas como las conductas problemáticas de las personas enfermas. En los familiares con EE baja se observó un mejor funcionamiento en el desempeño de tareas domésticas, en la demostración de afecto, en las actividades realizadas en el tiempo libre, en la conversación y en la demostración de apoyo entre el informante y el paciente. El modelo de estudio demostró que la mayor presencia de CS y el menor nivel de FS del paciente, fueron variables predictoras de una interacción familiar con características de mayor demostración de crítica, hostilidad y/o sobreinvolucramiento, que explicó 46% de la varianza con niveles de significancia estadística. <![CDATA[<b>Potenciales relacionados con eventos y comorbilidad en un grupo de adolescentes con trastorno por déficit de atención con hiperactividad</b>]]> http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S0185-33252008000300007&lng=es&nrm=iso&tlng=es Attention deficit hyperactivity disorder (ADHD) is a neuro-developmental disorder clinically characterized by three core symptoms: deficits in attentional processes, failure in inhibitory control -usually expressed through behavioral and cognitive impulsiveness-, and motor and verbal restlessness. Deficit in attentional resources is the main alteration in patients with this disorder. Attention can be considered as a neurocognitive state of neural preparation that precedes both perception and action. Attention focalizes consciousness in order to filter the constant flux of sensorial information, solve competence between stimuli for parallel processing and recruit and activate cerebral regions necessary to accomplish appropriate responses. Event-related potentials (ERPs) are a technique that has proven useful in the gathering of valuable information in the study of ADHD. One of the most studied ERPs is the P300 component. The most robust finding in the P300 research in ADHD is a decrease in the amplitude of the component in patients when compared to normal controls. This finding is usually interpreted as an evidence for a deficit in attention. ADHD usually presents commorbidity with several disorders; research shows that up to 87% of the children with ADHD present commorbidity with another disorder, up to 60% has either a behavioral or affective disorder commorbid with ADHD. Due to the wide range of disorders that are usually associated with this entity, it is useful in the research of commorbidity to use dimensional diagnostics, that is, a patient with ADHD may have commorbidity with an externalized disorder (EXT) (i.e. oppositionist defiant disorder); an internalized (INT) disorder (i.e. anxiety or affective disorder); or both an externalized and an internalized disorder (MIX). Commorbidity may have important implications in the electrophysiology of ADHD since no homogeneous results have been evident in the scarce research on the subject. Taking into account these considerations, the following experiment was designed in order to answer the question: Patients with the same main diagnostic, ADHD, but different commorbidities (INT and MIX) show different psychophysiological patterns of activation, as measured by ERPs to a continuous performance task? Sixteen patients diagnosed with ADHD by a specialist were recruited. Diagnosis was corroborated by a semi-structured interview, K-SADS-PL-MX, eight of them with an externalized comorbid (EXT) disorder, and eight of them with at least two comorbid disorders, one externalized an one internalized (MIX). A control group (CON) of eight normal subjects with no psychiatric diagnostic and matched by sex was also recruited. All subjects were between 13-16 years old with no history of Central Nervous System damage and normal IQ in the Weschler Intelligence Scale for Children. Brain electrical activity was recorded in the 19 derivations of the 10-20 international system while subjects executed a continuous performance task (CPT). Comparisons of behavioral data between groups showed some significant differences. A one-way ANOVA found differences between groups in the mean reaction time to the first part of the CPT and in the number of false positives in the second part. Electrophysiological data was analyzed with a non-parametrical multivariate test of permutations. When comparing responses to the frequent stimulus with responses to the infrequent, statistically significant differences were found in every subject; such differences share the topography and latency characteristics of the P3b component. When comparing the amplitude of this component between the groups, only two statistically significant differences were found. First, the EXT group presented a greater amplitude of the component elicited by the first part of the task in a latency of 425 to 445 msec in the parietal region of the medial line than the CON group. Second, also in response to the first part of the task, the amplitude of the CON group was bigger than that of the MIX group in a latency between 355 and 420 msec in the left temporal anterior region. No other comparison yielded significant results. When comparing between groups, mean reaction time to the first part of the task was the only behavioral variable that adequately distinguished control and patients. Even though controls executed significantly faster, they maintained the same efficacy as no differences were found in the number of errors or correct responses. This result is not surprising due to the fact that long reaction times usually denote inattention and so the fact that both groups of patients execute slower than the controls may be interpreted as a sign that, in spite of having different commorbidities, inattention is still a common problem in every patient of the sample. On the second part of the task, only the number of false positives showed statistically significant differences. However, in a posterior analysis of the data, it was evident that such differences were only between the EXT and the CON groups, with the EXT group presenting significantly more errors. False positives, especially on the second part of the task, are a measure of behavioral inhibition. Failure in inhibitory control is one of the three main symptoms of ADHD. However, some have proposed it as the main characteristic of the disorder. Analysis of the electrophysiological response to the first part of the task showed characteristic profiles of execution for each group. First, the P300 component was smaller in amplitude in the MIX group than in the control group and, even though differences were significant only in one derivation (T3), several other electrode sites more typically associated with the P300 component (C3, C4, P3, P4 and Pz) showed similar tendencies that did not reach statistical significance. Second, EXT patients had greater amplitude of the same P300 component in Pz than CON subjects. This result may seem to contradict most of the research on ADHD and P300. Nevertheless, considering the behavioral data, specially that no differences in correct responses were found between patients an controls, it is posible to assert that the greater amplitude of the component represents an overactive compensation in attentional circuits, necessary in the EXT group in order to execute at the same level of non-ADHD subjects. The results of this study present with information on a poorly reasearched subject: comorbidity and electrophysiology on ADHD.<hr/>La principal función afectada en el trastorno por déficit de atención con hiperactividad (TDAH) es la atención, la cual puede considerarse como un estado neurocognoscitivo cerebral de preparación que precede tanto a la percepción como a la acción. Los potenciales relacionados con eventos (PREs), una técnica útil en el estudio de la atención en esta entidad, pueden definirse como los cambios en la actividad eléctrica cerebral asociados temporalmente con la aparición de un evento, ya sea un estímulo o un proceso cognitivo. Con esta técnica es posible explorar las representaciones eléctricas de los procesos sensoriales y congnoscitivos con una alta resolución temporal. Uno de los PREs más estudiados en el TDAH es el P300, un componente positivo que ocurre en una latencia de alrededor de los 300 mseg. El hallazgo más contundente en el estudio del P300 en pacientes con TDAH es un decremento en la amplitud al compararlos con sujetos controles, lo cual suele ser interpretado como expresión de una atención deficiente. Por otro lado, el TDAH suele presentarse en comorbilidad con diferentes trastornos y siendo la presentación más infrecuente del síndrome es el TDAH <<puro>>. El presente estudio tiene como objetivo analizar si pacientes con el mismo diagnóstico principal, pero con diferente comorbilidad, presentan patrones de activación psicofisiológicos diferentes. Se evaluaron 16 pacientes diagnosticados con TDAH-M: ocho con comorbilidad EXT y ocho con comorbilidad MIX, así como ocho sujetos controles sanos. Tanto los pacientes como los controles realizaron las dos partes de una tarea de ejecución continua, mientras se registraba la actividad eléctrica cerebral en las 19 derivaciones del sistema internacional 10-20. En las medidas conductuales, las comparaciones intragrupos no arrrojaron diferencias estadísticamente significativas. Sin embargo, en las comparaciones entre grupos por medio de la prueba ANOVA de una vía sí aparecieron diferencias estadisticamente significativas (F=5.544 y p=0.012) entre los grupos en la media del tiempo de reacción en la parte 1 del CPT y en la variable errores por comisión en la parte 2 (F=3.975 y p=0.034). De las comparaciones electrofisiológicas realizadas entre grupos, sólo dos resultaron estadísticamente significativas. En primer lugar, el grupo EXT presentó mayor amplitud del componente que el grupo CON en una latencia entre 425-445 mseg en la región parietal media. En segundo lugar, el grupo CON tuvo mayor amplitud que el grupo MIX entre los 355-420 mseg en la región temporal anterior izquierda; ambos resultados se obtuvieron en la primera parte de la tarea. Ninguna otra comparación resultó significativa. Que el tiempo de reacción en la primera parte de la tarea fuera la única variable que distinguió entre pacientes y controles parece sugerir que, a pesar de que los pacientes tenían diferentes comorbilidades, la inatención sigue siendo el problema común a todos los pacientes de la muestra. La comparación de los datos electrofisiológicos entre grupos ofreció perfiles de ejecución característicos para cada subgrupo. Por un lado, el componente P300 fue de menor amplitud en los pacientes MIX que en los sujetos control (aunque sólo fue significativo en una derivación T3), lo cual concuerda con la bibliografía científica al respecto. Por otro, que los pacientes EXT presentaran mayor amplitud del componente P300 en Pz que los sujetos CON parece contrario a otros hallazgos de la bibliografía. Sin embargo, si se toma en cuenta que conductualmente tanto pacientes como controles ejecutaron al mismo nivel se puede sugerir que en los pacientes EXT el déficit de atención subyacente se compensa de manera exitosa y tal proceso se refleja en la amplitud de los PREs. Los resultados de este estudio proporcionan datos sobre cómo la comorbilidad incide en la respuesta electrofisiológica de los pacientes con TDAH. <![CDATA[<b>La melatonina</b>: <b>un coadyuvante potencial en el tratamiento de las demencias</b>]]> http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S0185-33252008000300008&lng=es&nrm=iso&tlng=es Alzheimer's disease is characterized by a progressive neuronal death and a lost of memory and cognition that unable the patient to perform daily tasks. Cytoskeleton alterations, identified as a major histopathologic hallmark of neurodegenerative diseases, occur in dementia. In this disease, neurons have pathologic inclusions containing fibrillar aggregates of hyperphosphorylated tau protein in absence of amyloid deposits. Abundant senile plaques and neurofibrillary tangles constitute the two major neuropathologic lesions present in hippocampal, neocortical, and forebrain cholinergic brain regions of Alzheimer's patients. Hyperphosphorylated tau and the subsequent formation of paired helical filaments loses the capabilities for maintaining highly asymmetrical neuronal polarity. Thus, in brains with a high content of hyperphosphorylated tau, microtubules are disassembled, the highly asymmetrical neural shape is lost and an impairment of axonal transport is produced together with a lost of dendrite arborizations. In addition, brain damage caused by free radicals occurs in Alzheimer's disease. This illness involves a reduction of the endogenous antioxidant enzyme system, increased senile-plaque formation, cytoskeletal collapse, and neuronal apoptosis induced by oxidative stress. Acetylcholinesterase inhibitors are the most commonly used compounds in the treatment of neurodegenerative diseases. However, despite their wide use in the treatment of Alzheimer's disease, these compounds have limited therapeutic effects and cause undesirable effects. Therefore it is necessary to investigate new alternatives in the Alzheimer's disease treatment. Considering that neurodegenerative diseases are cytoskeleton disorders, this cellular structure could be a drug target for therapeutic approaches by restoring normal cytoskeleton structure and by precluding damage caused by oxygen-reactive species. In this regard, melatonin, the indole secreted by the pineal gland during the dark phase of the photoperiod, has two important properties that may be useful for the treatment of mental disorders. One is that melatonin is a potent free-radical scavenger and the other is that this indole is a cytoskeletal modulator. A neuroprotective role for melatonin was initially suggested due to its free-radical scavenger properties. Melatonin detoxifies the highly toxic hydroxyl radical as well as the peroxyl radical, peroxynitrite anion, nitric oxide, and singlet oxygen, all of which can damage brain macromolecules. Moreover, melatonin stimulates the activity of antioxidative enzymes including superoxide dismutase, glutathione peroxidase, and glutathione reductase. Also, it is a lipophilic molecule able to cross the blood-brain barrier. All these properties make melatonin a highly effective pharmacologic agent against free-radical damage in the brain. Also, it is a useful neuroprotector in dementia because it synchronize the body rhythms with the photoperiod, which are altered in Alzheimer's disease and because normal circadian secretion of melatonin and sleep-wake cycle can be restored by the indolamine administration. Additionally, cytoskeletal modulation by melatonin is another relevant property of the indole for neurodegenerative diseases treatment. Direct assessment of melatonin effects on cytoskeletal organization in neuronal cells indicated that the indole promotes neuritogenesis in N1E-115 neuroblastoma cells at plasma melatonin concentration. Neurite formation is a complex process critical to establish synaptic connectivity that is lost in Alzheimer's disease. Neuritogenesis takes place by a dynamic cytoskeletal organization that involves microtubule enlargement, microfilament arrangement, and intermediate-filament reorganization. In particular, microtubule assembly participates in neurite formation elicited by melatonin through antagonism to calmodulin. Also, selective activation of protein kinase C (PKC) alpha by melatonin participates in vimentin intermediate filament rearrangements and actin dynamics for neurite outgrowth in neuroblastoma cells. In N1E-115 cells, melatonin at plasma and cerebrospinal fluid concentration caused an increase in microfilament arrays in stress fibers and their thickening, as well as increased growth cone formation, and augmented number of cells with microspikes. Recently, it was demonstrated that melatonin increased both the number of N1E-115 cells with filopodia and with long neurites through both PKC activation and Rho-associated kinase (ROCK) stimulation. The utility of melatonin to prevent damage in the cytoskeletal structure produced by neurodegenerative processes was demonstrated in N1E-115 neuroblastoma cells cultured with okadaic acid (OA), a specific inhibitor of the serine/threonine proteins phosphatases 1 and 2A that induces molecular and structural changes similar to those found in Alzheimer's disease. Melatonin prevented microtubule disruption followed by cell-shape changes and increased lipid peroxidation and apoptosis induced by OA. Melatonin effects on altered cytoskeletal organization induced by OA are dose-dependent and effects were observed at plasma -and cerebrospinal-fluid concentrations of the indole. These data support that melatonin can be useful in the treatment of neurodegenerative diseases by both its action on the cytoskeleton and by its free-radical scavenger properties.<hr/>La enfermedad de Alzheimer es una enfermedad neurodegenerativa progresiva que cursa con una deficiencia en las capacidades cognitivas, así como con la presencia de síntomas psiquiátricos y alteraciones conductuales. Las características histopatológicas más importantes en la enfermedad de Alzheimer son la formación de placas seniles, los ovillos neurofibrilares y un incremento en el estrés oxidativo. La polaridad estructural y la morfología neuronal se pierden en la enfermedad de Alzheimer. La proteína tau se encuentra anormalmente fosforilada, los microtúbulos se despolimerizan, se pierden la forma asimétrica de las neuronas y la conectividad sináptica, y se interrumpe el transporte axoplasmático. Asimismo, se ha sugerido que la inhibición o la pérdida en el balance de la formación de neuronas en el hipocampo puede participar en la fisiopatología de la enfermedad de Alzheimer debido a que el cerebro no puede reparar el daño neuronal y consecuentemente induce la pérdida de la cognición. Los agentes colinérgicos son los medicamentos más aceptados en el tratamiento de la enfermedad de Alzheimer en una etapa en que los síntomas se clasifican de medios a moderados. Sin embargo, el tratamiento de pacientes con enfermedad de Alzheimer grave es limitado. Por lo anterior se requiere la búsqueda de nuevas alternativas para el tratamiento de esta enfermedad. La melatonina es una indolamina que actúa como un potente antioxidante, como un modulador de la organización del citoesqueleto así como un factor de diferenciación celular. Diversos estudios han sugerido que la melatonina tiene un efecto neuroprotector por su capacidad de captar radicales libres. La melatonina disminuye la lipoperoxidación y la apoptosis producida por la administración de ácido ocadáico (AO) o peróxido de hidrógeno (H2O2). Se sabe que las especies reactivas de oxígeno producen alteraciones en la organización del citoesqueleto e influyen el estado de fosforilación de la proteína tau y que la melatonina previene la fosforilación de la proteína tau debido a su actividad antioxidante. Se ha descrito que la melatonina modula el arreglo de los microfilamentos de actina y la formación de fibras de tensión en las células Madin-Darby canine kidney (MDCK) por medio de una interacción concertada de la indolamina con la calmodulina y con la proteína cinasa C (PKC) y la participación de la proteína cinasa dependiente de Rho (ROCK). Asimismo, la melatonina participa en las etapas tempranas de la formación de neuritas en las células N1E-115 por medio de ROCK. Otros estudios han indicado que la melatonina previene el daño en el citoesqueleto producido por el AO en las células N1E-115. El AO se ha utilizado para reproducir en células en cultivo las alteraciones en el citoesqueleto y el incremento en el estrés oxidativo que ocurren en las neuronas de pacientes con enfermedad de Alzheimer. La melatonina en estas células previene la retracción del citoesqueleto, efecto del AO. La red del citoesqueleto se mantiene en el citoplasma y en las neuritas de las células N1E-115 cultivadas con melatonina, no obstante que sean tratadas con el AO posteriormente. Recientemente, se demostró que en las células de neuroblastoma N1E-115 incubadas con melatonina se previene la hiperfosforilación de la proteína tau causada por el AO. Aunado a lo anterior, se ha demostrado que la melatonina modula la formación de neuronas nuevas en un modelo in vitro utilizando células embrionarias y de corteza cerebral de ratón. La formación de neuronas inducida por la melatonina se corroboró utilizando células precursoras aisladas de animales adultos así como en animales adultos, y se encontró que la indolamina moduló la sobrevida de las células nuevas formadas, así como la diferenciación de éstas en neuronas nuevas. Las evidencias presentadas en esta revisión indican que la melatonina puede ser útil como un coadyuvante en el tratamiento de las demencias. <![CDATA[<b>La epigenética y los estudios en gemelos en el campo de la psiquiatría</b>]]> http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S0185-33252008000300009&lng=es&nrm=iso&tlng=es The sequence of the human genome integrates the keystone of our life. Part of it is transcribed to RNA, which in turn provides the information required by our cells to produce proteins. Discoveries in the genetics field have been essential to medicine and have been used to develop strategies to modify, prevent and propose new therapeutic approaches for human diseases. In the 19th Century, Gregor Johann Mendel developed a theoretical model which was able to predict in an accurate way hereditary mechanisms; indeed, his laws still explain the basis of human inheritance. Almost ninety years later, James Watson and Francis Crick announced their double-helix model of the DNA molecule. Then, positional cloning and the polymerase chain reaction (PCR) were introduced; more recently, almost 99% of the sequence of our genome was made public. The current period of time is known as the post-genomic era, due to the fact that researchers are not only obtaining the complete sequences of thousands of genomes, but are also searching for clues that may help understand the mechanisms that affect gene activation and deactivation, in which epigenetic factors are also involved. In medical domains, twins constitute a suitable group to study inherited disorders. Dizygotic or fraternal twins are produced by different egg and sperm cells, and even when these two fertilization events occur simultaneously, dizygotic twins share approximately the same percentage of genetic material than any pair of siblings, that is, around 50%. Some authors have suggested that the tendency for spontaneous dizygotic twinning could be attributed to a double ovulation which is genetically determined in an autosomal dominant manner. Monozygotic, as opposed to dizygotic twins, are produced by a single zygote whose cells are dissociated and originate two independent organisms; approximately a third of monozygotic twins are separated before the 5th day after fertilization, and the rest between the 5th and the 15th day. Most monozygotic twins are very similar; nevertheless, some few exceptions prove that in fact they actually do not have to be identical. Relatives of a person with a mental disorder tend to share traits associated with this disease, especially if the patient and the relative are monozygotic twins. However, important differences may be detected even between each pair of identical twins. Parameters such as concordance and heritability have shown that a monozygotic twin can develop an inherited disorder while his or her co-twin will always be disease-free. In addition to differences in susceptibility to inherited diseases, this kind of twins can display dissimilarities in somatic cell mutations (more overtly noticeable when ageing), their set of antibodies and T cell receptors, their number of mitochondrial DNA molecules, and chromosome X inactivation patterns in women, all of which are the main subject of many ongoing studies. A recent report shows that from 160 monozygotic twin pairs who were 3 to 74 years old, epigenetic patterns were identical early in life, but differences were more obvious at older ages, especially if twins were raised apart or if they had different medical history. Medical conditions, but also environmental factors such as pregnancy tobacco exposure, physical activity, and diet could contribute to differences in epigenetic patterns. It has been shown that epigenetic modifications (or epi-mutations) are more frequent than the ones that modify DNA sequence, so they are part of the fundamental causes of biological diversity, and they show how environment can modulate gene expression and contribute to our phenotype. Even when twin studies are sometimes considered purely genetic, they also give information about the influence of environmental factors. However, it is important to consider with caution the results from this type of studies. Heritability estimates are not unchangeable facts. They depend on the sample being analyzed, the genes involved in the specific sample, the characteristics of the environmental factors which members of this group were exposed to, and the precise moment the study was done. Epigenetics refers to changes that do not alter the DNA sequence but affect gene function due to chemical modifications which mainly occur in DNA cytosines and in chromatin-related histones. Epigenetic processes are covalent modifications which include the addition of functional groups (methyl, acetyl, phosphate, etc.) or proteins (ubiquitin, SUMO, etc.) to the DNA molecule or to associated proteins. These modifications contribute to the activation or inhibition of transcription, which leads to changes in messenger ARN expression that can ultimately influence the onset of disease. Pseudogenes are still being excluded while new genes are being confirmed in our genome sequence, but the current estimates indicate that each one of our nucleated cells contains almost 22000 genes (excluding mitochondrial DNA) which encode for polypeptides and more than 4,000 whose final product is RNA. Gene expression is partially controlled by DNA coiling around globular proteins called histones, which constitute a structure known as chromatin, a DNA-protein complex that represents the packaging of 3.25 billion base pairs of our genetic information. Physical and chemical chromatin modifications can also affect gene expression by changing DNA-protein interactions; in general terms, genes are inhibited when chromatin is packed and they are active when it is free. These dynamic states are controlled by epigenetic reversible modifications on DNA methylation or by changes in histones. It has been shown that subtle epigenetic differences between any two human beings are associated with dissimilar final chromatin remodeling, as well as expression/repression of genes.<hr/>La secuencia de ADN genómico que caracteriza a nuestra especie constituye la piedra fundamental de la vida humana; parte de ella se refleja en la secuencia del ARN y a través de éste se dicta la información necesaria para que nuestras células produzcan proteínas. La genética contribuye de manera importante a los avances en el campo médico. Los descubrimientos genéticos han permitido desarrollar estrategias para modificar, prevenir y proponer nuevas terapias para diversas enfermedades. En el siglo XIX, Gregor Johann Mendel desarrolló un modelo teórico capaz de predecir la naturaleza y propiedades de los mecanismos de la herencia, que sigue siendo indispensable para explicar la base de la herencia humana. Otro suceso determinante en la historia de la Medicina se dio a conocer casi nueve décadas después cuando James Watson y Francis Crick describieron su modelo estructural para el ADN. Posteriormente se introdujeron la clonación posicional y la reacción en cadena de la polimerasa; más recientemente se publicó cerca del 99% de la secuencia del genoma humano. El período actual se conoce como la era post-genómica, ya que además de descifrar genomas completos, los investigadores pretenden, entre otras cosas, esclarecer los mecanismos que influyen en la activación e inactivación de los genes, lo cual en parte involucra un nivel epigenético. En las ciencias médicas los gemelos constituyen un grupo idóneo para abordar el estudio de las enfermedades hereditarias. En este tipo de padecimientos suelen observarse similitudes entre parientes, en especial si se trata de gemelos monocigóticos. Sin embargo, aun en este tipo de hermanos se detectan diferencias importantes. Parámetros como los grados de concordancia y porcentajes de heredabilidad han puesto de manifiesto que un gemelo monocigótico puede presentar trastornos hereditarios que su co-gemelo nunca tendrá. La epigenética es el estudio de los cambios en la función de los genes que no afectan la secuencia del ADN, por modificaciones que tienen lugar principalmente en las citosinas de éste y en las histonas de la cromatina. Se ha determinado que las modificaciones epigenéticas son mucho más frecuentes que aquellas que modifican la secuencia del ADN, por lo que constituyen uno de los fundamentos de la diversidad biológica, muestran la manera en que el ambiente puede modular la expresión genética y contribuyen así a nuestro fenotipo. Esta revisión reúne datos sobre la posible relevancia de la epigenética en el estudio de los trastornos mentales y como posible explicación parcial de las diferencias observadas entre gemelos <<idénticos>>. Un conocimiento más profundo de los patrones epigenéticos podría contribuir a identificar factores de riesgo para estos trastornos. <![CDATA[<b>La conciencia y el cerebro</b>: <b>a propósito de <i>La Flama Misteriosa</i></b>]]> http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S0185-33252008000300010&lng=es&nrm=iso&tlng=es The sequence of the human genome integrates the keystone of our life. Part of it is transcribed to RNA, which in turn provides the information required by our cells to produce proteins. Discoveries in the genetics field have been essential to medicine and have been used to develop strategies to modify, prevent and propose new therapeutic approaches for human diseases. In the 19th Century, Gregor Johann Mendel developed a theoretical model which was able to predict in an accurate way hereditary mechanisms; indeed, his laws still explain the basis of human inheritance. Almost ninety years later, James Watson and Francis Crick announced their double-helix model of the DNA molecule. Then, positional cloning and the polymerase chain reaction (PCR) were introduced; more recently, almost 99% of the sequence of our genome was made public. The current period of time is known as the post-genomic era, due to the fact that researchers are not only obtaining the complete sequences of thousands of genomes, but are also searching for clues that may help understand the mechanisms that affect gene activation and deactivation, in which epigenetic factors are also involved. In medical domains, twins constitute a suitable group to study inherited disorders. Dizygotic or fraternal twins are produced by different egg and sperm cells, and even when these two fertilization events occur simultaneously, dizygotic twins share approximately the same percentage of genetic material than any pair of siblings, that is, around 50%. Some authors have suggested that the tendency for spontaneous dizygotic twinning could be attributed to a double ovulation which is genetically determined in an autosomal dominant manner. Monozygotic, as opposed to dizygotic twins, are produced by a single zygote whose cells are dissociated and originate two independent organisms; approximately a third of monozygotic twins are separated before the 5th day after fertilization, and the rest between the 5th and the 15th day. Most monozygotic twins are very similar; nevertheless, some few exceptions prove that in fact they actually do not have to be identical. Relatives of a person with a mental disorder tend to share traits associated with this disease, especially if the patient and the relative are monozygotic twins. However, important differences may be detected even between each pair of identical twins. Parameters such as concordance and heritability have shown that a monozygotic twin can develop an inherited disorder while his or her co-twin will always be disease-free. In addition to differences in susceptibility to inherited diseases, this kind of twins can display dissimilarities in somatic cell mutations (more overtly noticeable when ageing), their set of antibodies and T cell receptors, their number of mitochondrial DNA molecules, and chromosome X inactivation patterns in women, all of which are the main subject of many ongoing studies. A recent report shows that from 160 monozygotic twin pairs who were 3 to 74 years old, epigenetic patterns were identical early in life, but differences were more obvious at older ages, especially if twins were raised apart or if they had different medical history. Medical conditions, but also environmental factors such as pregnancy tobacco exposure, physical activity, and diet could contribute to differences in epigenetic patterns. It has been shown that epigenetic modifications (or epi-mutations) are more frequent than the ones that modify DNA sequence, so they are part of the fundamental causes of biological diversity, and they show how environment can modulate gene expression and contribute to our phenotype. Even when twin studies are sometimes considered purely genetic, they also give information about the influence of environmental factors. However, it is important to consider with caution the results from this type of studies. Heritability estimates are not unchangeable facts. They depend on the sample being analyzed, the genes involved in the specific sample, the characteristics of the environmental factors which members of this group were exposed to, and the precise moment the study was done. Epigenetics refers to changes that do not alter the DNA sequence but affect gene function due to chemical modifications which mainly occur in DNA cytosines and in chromatin-related histones. Epigenetic processes are covalent modifications which include the addition of functional groups (methyl, acetyl, phosphate, etc.) or proteins (ubiquitin, SUMO, etc.) to the DNA molecule or to associated proteins. These modifications contribute to the activation or inhibition of transcription, which leads to changes in messenger ARN expression that can ultimately influence the onset of disease. Pseudogenes are still being excluded while new genes are being confirmed in our genome sequence, but the current estimates indicate that each one of our nucleated cells contains almost 22000 genes (excluding mitochondrial DNA) which encode for polypeptides and more than 4,000 whose final product is RNA. Gene expression is partially controlled by DNA coiling around globular proteins called histones, which constitute a structure known as chromatin, a DNA-protein complex that represents the packaging of 3.25 billion base pairs of our genetic information. Physical and chemical chromatin modifications can also affect gene expression by changing DNA-protein interactions; in general terms, genes are inhibited when chromatin is packed and they are active when it is free. These dynamic states are controlled by epigenetic reversible modifications on DNA methylation or by changes in histones. It has been shown that subtle epigenetic differences between any two human beings are associated with dissimilar final chromatin remodeling, as well as expression/repression of genes.<hr/>La secuencia de ADN genómico que caracteriza a nuestra especie constituye la piedra fundamental de la vida humana; parte de ella se refleja en la secuencia del ARN y a través de éste se dicta la información necesaria para que nuestras células produzcan proteínas. La genética contribuye de manera importante a los avances en el campo médico. Los descubrimientos genéticos han permitido desarrollar estrategias para modificar, prevenir y proponer nuevas terapias para diversas enfermedades. En el siglo XIX, Gregor Johann Mendel desarrolló un modelo teórico capaz de predecir la naturaleza y propiedades de los mecanismos de la herencia, que sigue siendo indispensable para explicar la base de la herencia humana. Otro suceso determinante en la historia de la Medicina se dio a conocer casi nueve décadas después cuando James Watson y Francis Crick describieron su modelo estructural para el ADN. Posteriormente se introdujeron la clonación posicional y la reacción en cadena de la polimerasa; más recientemente se publicó cerca del 99% de la secuencia del genoma humano. El período actual se conoce como la era post-genómica, ya que además de descifrar genomas completos, los investigadores pretenden, entre otras cosas, esclarecer los mecanismos que influyen en la activación e inactivación de los genes, lo cual en parte involucra un nivel epigenético. En las ciencias médicas los gemelos constituyen un grupo idóneo para abordar el estudio de las enfermedades hereditarias. En este tipo de padecimientos suelen observarse similitudes entre parientes, en especial si se trata de gemelos monocigóticos. Sin embargo, aun en este tipo de hermanos se detectan diferencias importantes. Parámetros como los grados de concordancia y porcentajes de heredabilidad han puesto de manifiesto que un gemelo monocigótico puede presentar trastornos hereditarios que su co-gemelo nunca tendrá. La epigenética es el estudio de los cambios en la función de los genes que no afectan la secuencia del ADN, por modificaciones que tienen lugar principalmente en las citosinas de éste y en las histonas de la cromatina. Se ha determinado que las modificaciones epigenéticas son mucho más frecuentes que aquellas que modifican la secuencia del ADN, por lo que constituyen uno de los fundamentos de la diversidad biológica, muestran la manera en que el ambiente puede modular la expresión genética y contribuyen así a nuestro fenotipo. Esta revisión reúne datos sobre la posible relevancia de la epigenética en el estudio de los trastornos mentales y como posible explicación parcial de las diferencias observadas entre gemelos <<idénticos>>. Un conocimiento más profundo de los patrones epigenéticos podría contribuir a identificar factores de riesgo para estos trastornos. <![CDATA[<b>Brüne M., Brüne-Cohrs U., McGrew W.C., Preuschoft S. Psicopatología en grandes antropoides</b>: <b>Conceptos, opciones de tratamiento y posibles semejanzas con los trastornos psiquiátricos humanos</b>]]> http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S0185-33252008000300011&lng=es&nrm=iso&tlng=es The sequence of the human genome integrates the keystone of our life. Part of it is transcribed to RNA, which in turn provides the information required by our cells to produce proteins. Discoveries in the genetics field have been essential to medicine and have been used to develop strategies to modify, prevent and propose new therapeutic approaches for human diseases. In the 19th Century, Gregor Johann Mendel developed a theoretical model which was able to predict in an accurate way hereditary mechanisms; indeed, his laws still explain the basis of human inheritance. Almost ninety years later, James Watson and Francis Crick announced their double-helix model of the DNA molecule. Then, positional cloning and the polymerase chain reaction (PCR) were introduced; more recently, almost 99% of the sequence of our genome was made public. The current period of time is known as the post-genomic era, due to the fact that researchers are not only obtaining the complete sequences of thousands of genomes, but are also searching for clues that may help understand the mechanisms that affect gene activation and deactivation, in which epigenetic factors are also involved. In medical domains, twins constitute a suitable group to study inherited disorders. Dizygotic or fraternal twins are produced by different egg and sperm cells, and even when these two fertilization events occur simultaneously, dizygotic twins share approximately the same percentage of genetic material than any pair of siblings, that is, around 50%. Some authors have suggested that the tendency for spontaneous dizygotic twinning could be attributed to a double ovulation which is genetically determined in an autosomal dominant manner. Monozygotic, as opposed to dizygotic twins, are produced by a single zygote whose cells are dissociated and originate two independent organisms; approximately a third of monozygotic twins are separated before the 5th day after fertilization, and the rest between the 5th and the 15th day. Most monozygotic twins are very similar; nevertheless, some few exceptions prove that in fact they actually do not have to be identical. Relatives of a person with a mental disorder tend to share traits associated with this disease, especially if the patient and the relative are monozygotic twins. However, important differences may be detected even between each pair of identical twins. Parameters such as concordance and heritability have shown that a monozygotic twin can develop an inherited disorder while his or her co-twin will always be disease-free. In addition to differences in susceptibility to inherited diseases, this kind of twins can display dissimilarities in somatic cell mutations (more overtly noticeable when ageing), their set of antibodies and T cell receptors, their number of mitochondrial DNA molecules, and chromosome X inactivation patterns in women, all of which are the main subject of many ongoing studies. A recent report shows that from 160 monozygotic twin pairs who were 3 to 74 years old, epigenetic patterns were identical early in life, but differences were more obvious at older ages, especially if twins were raised apart or if they had different medical history. Medical conditions, but also environmental factors such as pregnancy tobacco exposure, physical activity, and diet could contribute to differences in epigenetic patterns. It has been shown that epigenetic modifications (or epi-mutations) are more frequent than the ones that modify DNA sequence, so they are part of the fundamental causes of biological diversity, and they show how environment can modulate gene expression and contribute to our phenotype. Even when twin studies are sometimes considered purely genetic, they also give information about the influence of environmental factors. However, it is important to consider with caution the results from this type of studies. Heritability estimates are not unchangeable facts. They depend on the sample being analyzed, the genes involved in the specific sample, the characteristics of the environmental factors which members of this group were exposed to, and the precise moment the study was done. Epigenetics refers to changes that do not alter the DNA sequence but affect gene function due to chemical modifications which mainly occur in DNA cytosines and in chromatin-related histones. Epigenetic processes are covalent modifications which include the addition of functional groups (methyl, acetyl, phosphate, etc.) or proteins (ubiquitin, SUMO, etc.) to the DNA molecule or to associated proteins. These modifications contribute to the activation or inhibition of transcription, which leads to changes in messenger ARN expression that can ultimately influence the onset of disease. Pseudogenes are still being excluded while new genes are being confirmed in our genome sequence, but the current estimates indicate that each one of our nucleated cells contains almost 22000 genes (excluding mitochondrial DNA) which encode for polypeptides and more than 4,000 whose final product is RNA. Gene expression is partially controlled by DNA coiling around globular proteins called histones, which constitute a structure known as chromatin, a DNA-protein complex that represents the packaging of 3.25 billion base pairs of our genetic information. Physical and chemical chromatin modifications can also affect gene expression by changing DNA-protein interactions; in general terms, genes are inhibited when chromatin is packed and they are active when it is free. These dynamic states are controlled by epigenetic reversible modifications on DNA methylation or by changes in histones. It has been shown that subtle epigenetic differences between any two human beings are associated with dissimilar final chromatin remodeling, as well as expression/repression of genes.<hr/>La secuencia de ADN genómico que caracteriza a nuestra especie constituye la piedra fundamental de la vida humana; parte de ella se refleja en la secuencia del ARN y a través de éste se dicta la información necesaria para que nuestras células produzcan proteínas. La genética contribuye de manera importante a los avances en el campo médico. Los descubrimientos genéticos han permitido desarrollar estrategias para modificar, prevenir y proponer nuevas terapias para diversas enfermedades. En el siglo XIX, Gregor Johann Mendel desarrolló un modelo teórico capaz de predecir la naturaleza y propiedades de los mecanismos de la herencia, que sigue siendo indispensable para explicar la base de la herencia humana. Otro suceso determinante en la historia de la Medicina se dio a conocer casi nueve décadas después cuando James Watson y Francis Crick describieron su modelo estructural para el ADN. Posteriormente se introdujeron la clonación posicional y la reacción en cadena de la polimerasa; más recientemente se publicó cerca del 99% de la secuencia del genoma humano. El período actual se conoce como la era post-genómica, ya que además de descifrar genomas completos, los investigadores pretenden, entre otras cosas, esclarecer los mecanismos que influyen en la activación e inactivación de los genes, lo cual en parte involucra un nivel epigenético. En las ciencias médicas los gemelos constituyen un grupo idóneo para abordar el estudio de las enfermedades hereditarias. En este tipo de padecimientos suelen observarse similitudes entre parientes, en especial si se trata de gemelos monocigóticos. Sin embargo, aun en este tipo de hermanos se detectan diferencias importantes. Parámetros como los grados de concordancia y porcentajes de heredabilidad han puesto de manifiesto que un gemelo monocigótico puede presentar trastornos hereditarios que su co-gemelo nunca tendrá. La epigenética es el estudio de los cambios en la función de los genes que no afectan la secuencia del ADN, por modificaciones que tienen lugar principalmente en las citosinas de éste y en las histonas de la cromatina. Se ha determinado que las modificaciones epigenéticas son mucho más frecuentes que aquellas que modifican la secuencia del ADN, por lo que constituyen uno de los fundamentos de la diversidad biológica, muestran la manera en que el ambiente puede modular la expresión genética y contribuyen así a nuestro fenotipo. Esta revisión reúne datos sobre la posible relevancia de la epigenética en el estudio de los trastornos mentales y como posible explicación parcial de las diferencias observadas entre gemelos <<idénticos>>. Un conocimiento más profundo de los patrones epigenéticos podría contribuir a identificar factores de riesgo para estos trastornos. <![CDATA[<b>Autoevaluación</b>]]> http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S0185-33252008000300012&lng=es&nrm=iso&tlng=es The sequence of the human genome integrates the keystone of our life. Part of it is transcribed to RNA, which in turn provides the information required by our cells to produce proteins. Discoveries in the genetics field have been essential to medicine and have been used to develop strategies to modify, prevent and propose new therapeutic approaches for human diseases. In the 19th Century, Gregor Johann Mendel developed a theoretical model which was able to predict in an accurate way hereditary mechanisms; indeed, his laws still explain the basis of human inheritance. Almost ninety years later, James Watson and Francis Crick announced their double-helix model of the DNA molecule. Then, positional cloning and the polymerase chain reaction (PCR) were introduced; more recently, almost 99% of the sequence of our genome was made public. The current period of time is known as the post-genomic era, due to the fact that researchers are not only obtaining the complete sequences of thousands of genomes, but are also searching for clues that may help understand the mechanisms that affect gene activation and deactivation, in which epigenetic factors are also involved. In medical domains, twins constitute a suitable group to study inherited disorders. Dizygotic or fraternal twins are produced by different egg and sperm cells, and even when these two fertilization events occur simultaneously, dizygotic twins share approximately the same percentage of genetic material than any pair of siblings, that is, around 50%. Some authors have suggested that the tendency for spontaneous dizygotic twinning could be attributed to a double ovulation which is genetically determined in an autosomal dominant manner. Monozygotic, as opposed to dizygotic twins, are produced by a single zygote whose cells are dissociated and originate two independent organisms; approximately a third of monozygotic twins are separated before the 5th day after fertilization, and the rest between the 5th and the 15th day. Most monozygotic twins are very similar; nevertheless, some few exceptions prove that in fact they actually do not have to be identical. Relatives of a person with a mental disorder tend to share traits associated with this disease, especially if the patient and the relative are monozygotic twins. However, important differences may be detected even between each pair of identical twins. Parameters such as concordance and heritability have shown that a monozygotic twin can develop an inherited disorder while his or her co-twin will always be disease-free. In addition to differences in susceptibility to inherited diseases, this kind of twins can display dissimilarities in somatic cell mutations (more overtly noticeable when ageing), their set of antibodies and T cell receptors, their number of mitochondrial DNA molecules, and chromosome X inactivation patterns in women, all of which are the main subject of many ongoing studies. A recent report shows that from 160 monozygotic twin pairs who were 3 to 74 years old, epigenetic patterns were identical early in life, but differences were more obvious at older ages, especially if twins were raised apart or if they had different medical history. Medical conditions, but also environmental factors such as pregnancy tobacco exposure, physical activity, and diet could contribute to differences in epigenetic patterns. It has been shown that epigenetic modifications (or epi-mutations) are more frequent than the ones that modify DNA sequence, so they are part of the fundamental causes of biological diversity, and they show how environment can modulate gene expression and contribute to our phenotype. Even when twin studies are sometimes considered purely genetic, they also give information about the influence of environmental factors. However, it is important to consider with caution the results from this type of studies. Heritability estimates are not unchangeable facts. They depend on the sample being analyzed, the genes involved in the specific sample, the characteristics of the environmental factors which members of this group were exposed to, and the precise moment the study was done. Epigenetics refers to changes that do not alter the DNA sequence but affect gene function due to chemical modifications which mainly occur in DNA cytosines and in chromatin-related histones. Epigenetic processes are covalent modifications which include the addition of functional groups (methyl, acetyl, phosphate, etc.) or proteins (ubiquitin, SUMO, etc.) to the DNA molecule or to associated proteins. These modifications contribute to the activation or inhibition of transcription, which leads to changes in messenger ARN expression that can ultimately influence the onset of disease. Pseudogenes are still being excluded while new genes are being confirmed in our genome sequence, but the current estimates indicate that each one of our nucleated cells contains almost 22000 genes (excluding mitochondrial DNA) which encode for polypeptides and more than 4,000 whose final product is RNA. Gene expression is partially controlled by DNA coiling around globular proteins called histones, which constitute a structure known as chromatin, a DNA-protein complex that represents the packaging of 3.25 billion base pairs of our genetic information. Physical and chemical chromatin modifications can also affect gene expression by changing DNA-protein interactions; in general terms, genes are inhibited when chromatin is packed and they are active when it is free. These dynamic states are controlled by epigenetic reversible modifications on DNA methylation or by changes in histones. It has been shown that subtle epigenetic differences between any two human beings are associated with dissimilar final chromatin remodeling, as well as expression/repression of genes.<hr/>La secuencia de ADN genómico que caracteriza a nuestra especie constituye la piedra fundamental de la vida humana; parte de ella se refleja en la secuencia del ARN y a través de éste se dicta la información necesaria para que nuestras células produzcan proteínas. La genética contribuye de manera importante a los avances en el campo médico. Los descubrimientos genéticos han permitido desarrollar estrategias para modificar, prevenir y proponer nuevas terapias para diversas enfermedades. En el siglo XIX, Gregor Johann Mendel desarrolló un modelo teórico capaz de predecir la naturaleza y propiedades de los mecanismos de la herencia, que sigue siendo indispensable para explicar la base de la herencia humana. Otro suceso determinante en la historia de la Medicina se dio a conocer casi nueve décadas después cuando James Watson y Francis Crick describieron su modelo estructural para el ADN. Posteriormente se introdujeron la clonación posicional y la reacción en cadena de la polimerasa; más recientemente se publicó cerca del 99% de la secuencia del genoma humano. El período actual se conoce como la era post-genómica, ya que además de descifrar genomas completos, los investigadores pretenden, entre otras cosas, esclarecer los mecanismos que influyen en la activación e inactivación de los genes, lo cual en parte involucra un nivel epigenético. En las ciencias médicas los gemelos constituyen un grupo idóneo para abordar el estudio de las enfermedades hereditarias. En este tipo de padecimientos suelen observarse similitudes entre parientes, en especial si se trata de gemelos monocigóticos. Sin embargo, aun en este tipo de hermanos se detectan diferencias importantes. Parámetros como los grados de concordancia y porcentajes de heredabilidad han puesto de manifiesto que un gemelo monocigótico puede presentar trastornos hereditarios que su co-gemelo nunca tendrá. La epigenética es el estudio de los cambios en la función de los genes que no afectan la secuencia del ADN, por modificaciones que tienen lugar principalmente en las citosinas de éste y en las histonas de la cromatina. Se ha determinado que las modificaciones epigenéticas son mucho más frecuentes que aquellas que modifican la secuencia del ADN, por lo que constituyen uno de los fundamentos de la diversidad biológica, muestran la manera en que el ambiente puede modular la expresión genética y contribuyen así a nuestro fenotipo. Esta revisión reúne datos sobre la posible relevancia de la epigenética en el estudio de los trastornos mentales y como posible explicación parcial de las diferencias observadas entre gemelos <<idénticos>>. Un conocimiento más profundo de los patrones epigenéticos podría contribuir a identificar factores de riesgo para estos trastornos.