Background:

Major Depressive Disorder (MDD) is a disease associated to emotional, vegetative and physical symptoms, including for the latter those pain-related symptoms. MDD has a high prevalence rate with a substantial burden of illness, and it expected that by 2020 it will become the second cause of world disability. The diagnosis of MDD is difficult due to the high prevalence of painful physical symptoms, and also due to the fact these symptoms are more evident that the embedded emotional ones. Over 76% of patients with MDD, report painful physical symptoms observed, like headache, abdominal pain, back pain and unspecific-located pain; observing these symptoms can even predict depression severity. In addition, the likelihood of psychiatric disease increases, importantly, with the number of physical symptoms observed; moreover, the remission of physical symptoms predicts the complete remission in MDD. We present an observational, prospective study to examine the clinical profile of Mexican outpatients suffering MDD and determine the relationship between depression severity, painful physical symptoms in quality of life and depression.

Methods:

Adult patients with current episodes of MDD, treated with antidepressants were included. MDD was defined according to the criteria of the Statistical Manual of Mental Disorders - 4th Edition (DSM-IV) or in the International Classification of Diseases and Related Health Problems, 10th Revision (ICD-10). Patients should have been free of depression symptoms prior to the current episode for at least 2 months. Duration of current episode should not exceed two years. Treatment-resistant patients and those with other psychiatric diagnosis were excluded. Treatment-resistance was defined as: a) a failure to respond to treatment when two different antidepressants were employed at therapeutic doses for at least four weeks each, b) when the subject was previously treated with IMAO inhibitors, c) when electro-convulsive therapy (ECT) was previously employed. Other exclusion criteria comprise previous or current diagnosis of schizophrenia, schizophreniform or schizoaffective disorder, bipolar disorder, dementia or mental impairment. Patients were selected in 34 centers in Mexico.

Patients were classified according to the presence (SFD+) or absence (SFD-) of painful physical symptoms using the Somatic Symptom Inventory (SSI); SFD+ was defined as scores ≥ 2 for the pain-related items in the SSI (items 2, 3, 9, 14, 19, 27 and 28). Visual Analogue Scale (VAS) quantified pain severity (cervical pain, headache, back pain, shoulder pain, interference of pain in daily activities and vigil-time with pain). HAMD17 and CGI-S determined depression severity, while the Quality of Life in Depression Scale (QLDS) quantified subjective well-being.

Linear regression models were employed to compare groups for VAS, HAMD17, CGI-S, and QLDS, to fit the confusions or clinical predictors when needed. Proportions between groups were established with Fisher exact test or logistic regression. Significance levels were established at 0.005 due to the observational nature of the study. In the result tables, standard deviation (SD) is reported as a variation around the mean value as Mean ± SD, and 95% confidence intervals are denoted 95% IC.

Results:

A total of 313 patients were enrolled in the study. All of the enrolled patients were Mexican, almost them were women and had at least a previous MDD episode. Painful physical symptoms were reported by 73.7% of patients, these patients were classified into the SFD+ group. Neither statistical nor clinical significant differences between the SFD+ and SFD- groups were found when analyzing socio-demographic variables (age, gender, ethnical origin) and disease history variables (number of previous episodes of MDD, in the last 24 months, duration of current episode).

At baseline, patients had a CGI-S mean score of 4.6 and HAMD17 of 26.3. HAMD17 mean score (27.1) in SFD+ patients was significantly higher (p<0.0001) than the SFD- patients (23.8), but nonsignificant differences between groups were found for the subscales central, Maier & retard. CGI-S scores were similar between SFD+ and SFD-; 4.6 and 4.5 respectively (p>0.05). Prevalent painful physical symptoms were also the most painful, when a five-point scale was employed to measure severity, and comprised muscular pain (84.9%), cervical pain (84.2%) and headache (83.5%). SFD+ patients had higher pain severity in all VAS scales (p<0.0001), with perceived severity scores twice as large when compared to SFDgroup. In particular, the global pain VAS reported average values of 49.0 and 19.7 for the SFD+ and SFD- groups respectively.

Patients came to the first psychiatric consultation treated with psychotherapy (27.9%), antidepressants (37.3%), anxiolytics (28.6%) and analgesics (9.7%); more than 50% of all patients were not taking any drugs or receiving psychotherapy for treatment of MDD at baseline. Analgesics were used only by 9.7% of patients for the treatment of painful physical symptoms in their current MDD episode. No significant differences between groups were found when comparing the use of psychotherapy, antidepressants, anxiolytics, antipsychotics, mood stabilizers or analgesics. Quality of life was poor for all patients, but significantly worse in the SFD+ group than in the SFD- group (QLDS scores of 23.2 and 20.0 respectively, p<0.001).

Discussion: The diagnosis and symptoms manifestation can be influenced by local socio-cultural factors, in particular cultural differences are associated with the prevalence of painful physical symptoms, but this finding is not consistent. The results of this study can be extrapolated to the MDD Mexican population, as selection criteria comprised only operative diagnosis criteria, and not enrollment into the study took place due to the presence of painful physical symptoms. Patients included into the study presented a moderate to severe disease as measured with the HAMD17 scores. The high prevalence of painful physical symptoms in patients with depression was confirmed in this study; it has been reported the patients report pain-related symptoms as the main (even the only) symptom when consulting general practitioners. Painful physical symptoms in MDD include headache, cervical pain, back pain or neck pain; the presence of painful physical symptoms in depression is associated to higher intakes medication, but in this study more than 50% of subjects were not receiving any treatment, including psychotherapy.

The treatment of MDD is by no means optimal, as only 30%- 40% of these patients reach complete remission of symptoms with their first antidepressant. Psychological symptoms respond to antidepressant treatment, but in general, this is not the case for the physical symptoms. The lack of efficacy can be explained as a failure in the treatment of these painful physical symptoms. Resolving these symptoms is even a predictor for the complete remission of MDD; the evidence might suggest that treatment of emotional and physical manifestations of depression could improve successful-treatment rates.

Conclusion: As found in other reports, a high prevalence of painful physical symptoms was found in MDD patients. Increase in pain severity is associated with higher HAMD17 scores but not CGI-S scores; this discrepancy in the final rates obtained with both scales suggests that both emotional and physical dimensions of MDD should be considered when the clinical assessment is performed. We concluded that clinical judgment of Mexican psychiatrists differs between their global impression and a semi-structured interview in the same patient and therefore is fundamental that the clinical evaluation consists of both emotional and physical manifestations as important components of MDD.

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