Data source, search strategy, and research questions

No previous systematic review that focused on this phenomenon of interest was found after a comprehensive search in the PROSPERO database. Thus, this review was not registered in the International Prospective Register of Systematic Reviews, since according to the National Institute of Health Research, scoping reviews are ineligible for registration into PROSPERO. A review of literature was undertaken to identify all relevant publications concerning the overlap of OCD and PTSD symptomatology. We followed the PRISMA-ScR Statement (^{Moher et al., 2009}), and the following research questions were formulated: 1. Does a functional connection exist between OCD and PTSD symptoms? 2. Which variables (e.g., risk factors, clinical similarities, treatment implications, etc.) influence the treatment outcomes of patients with mutual OCD and PTSD symptom clusters? Consequently, two independent authors searched PubMed, PsycINFO, and Web of Science databases between April 01 and July 26, 2020. The search was made from inception through July 26, 2020 using the following terms: (overlap of) AND (symptoms OR symptomatology); (OCD) OR (obsessive OR compulsive) AND (PTSD) OR (posttraumatic OR trauma); (“humans”[Mesh]AND “comorbidity”[Mesh]); (“Obsessive-Compulsive Disorder / diagnosis”[Mesh]) AND “Obsessive-Compulsive Disorder / epidemiology”[Mesh] AND “Obsessive-Compulsive Disorder / psychology” [Mesh]); (“Stress Disorders, Post-Traumatic / diagnosis”[Mesh]) AND (“Stress Disorders, Post-Traumatic / epidemiology”[Mesh] AND “Stress Disorders, Post-Traumatic / psychology” [Mesh]).

Eligibility criteria

Initially, we restricted our literature search to include articles that met the following criteria according to the key words mentioned above: studies published in English in peer reviewed journals that contributed quantitative or qualitative data and that specifically addressed the relationship between OCD and PTSD symptoms as the main aim or outcome of the study. Secondly, non-peer-reviewed articles, studies that did not address this phenomenon of interest and gray literature documents were excluded. Thirdly, we eliminated all duplicate findings from these searches following a title and abstract review. Lastly, the reference lists of all articles that were relevant, as well as any recent review papers that examined this phenomenon, were surveyed in full detail to determine if they met our inclusion criteria. No other conditions than those previously described were applied to our study selection. Most initial search results (2,784) were excluded because of unrelatedness in the title or abstract regarding our subject matter (e.g., “traumatic brain injury,” “surgical trauma,” “compulsive exercise” etc.), and thus, the search resulted in 103 articles for further review. After additional inquiry, we narrowed these articles down to 25 relevant to the present study. Data and biases from these studies were scrutinized using critical appraisal tools, such as the Newcastle-Ottawa Scale for cross sectional, retrospective and cohort studies, and the Joanna Briggs Institute’s Critical Appraisal Tools for case series and case reports (^{Jordan, Lockwood, Munn, & Aromataris, 2019}; ^{Stang, 2010}). Pertaining to their methodological approach, we included 11 cross-sectional studies, five longitudinal-prospective studies, four case series, four case studies and one retrospective study. Ultimately, all included studies were read, and key pieces of information were extracted, considering their sample size, recruitment process, design, outcomes, measures, psychometric tools used, main results, and consequences for future research.

Analysis

We did not conduct any statistical test or meta-analysis because of methodological disparities between the included studies. Likewise, weighting the studies was not possible or done because articles with distinct methodological approaches and properties were utilized. Taking this into account, both authors chose to examine the extent, range, and characteristics of the found evidence of this phenomenon of interest. This effort meant to summarize findings from this body of knowledge that is heterogeneous in its methods and facilitated the identification of gaps in the literature to aid the planning and commissioning of future research. Thus, a thematic synthesis was done employing the data extracted, since scoping reviews is a type of knowledge synthesis that follows a systematic approach to further map evidence on a topic, helping to identify main concepts, theories, and knowledge gaps that may inspire further innovative research (Figure 1).    

Figure 1 Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) flow diagram of the review process. 

Clinical domains (n = 7)

Several of the included studies addressed phenomenological and symptomatic domains of OCD and PTSD symptoms in a variety of community samples. These reports were mostly comprised of observational studies or clinical cases. To start with, relatively recent literature has showcased PTSD patients that manifest cognitions such as compulsions that have been described to occur strictly within the context of trauma, and that these may not be necessarily indicative of a comorbid diagnosis of OCD (^{de Silva & Marks, 2001}). Similarly, other researchers have noticed that adults with intrusive cognitions tend to be more aware of specific external or internal stimuli in comparison to other adults with obsessions. Also, it was observed that worry, as a dimensional cognition, tends to be more severe than dysfunction-generating obsessions (^{Langlois, Freeston, & Ladouceur, 2000}). Coincidentally, mental images, a recurrent phenomenon in many anxiety disorders, tend to be portrayed as irrational in nature in OCD patients. In comparison, it is important to note that individuals with this diagnosis can also experience intrusive images associated with earlier trauma (^{Speckens et al., 2007}). Likewise, checking behaviors, another symptomatic dimension in obsessive and anxiety disorders, have been noted in a sample of motor vehicle accident survivors with up to six months post-trauma (^{Ehring, Ehlers, & Glucksman, 2008}). In regards to a possible temporal causality factor, another study found that nearly all OCD symptoms were more frequent or severe among posttraumatic OCD patients, with the exceptions of certain symptomatic domains, such as symmetry-seeking behaviors, hand washing, and hypersensitivity to specific sensory phenomena, and that these symptoms were more common in pretraumatic OCD (^{Fontenelle et al., 2012}). In the same way, another study about civilian survivors of war found that compulsive washing was the most frequent and severe symptom in participants with high levels of PTSD symptoms (^{Morina et al., 2016}). Likewise, some researchers found a similar thematic connection in an outpatient sample of veterans with OCD self-report. These results may show that some OCD symptom profiles could be similar to PTSD cognitive symptom clusters (e.g., feeling responsible for harm, and unacceptable violent, or sexual thoughts; ^{Franklin & Raines, 2019}).

Risk factors and other correlates (n = 9)

Several findings included in this review discussed the relevance of specific stressors that resulted in the development of OCD symptoms in PTSD patients. Of interest, an old case report describes an individual without previous overt psychopathology who, after experiencing combat stressors, underwent development of concurrent OCD and PTSD, showing classical symptoms, such as obsessions of violent nature, contamination, doubt, compulsive hand-washing, cleaning, checking, counting, touching, attempts to resist these compulsions, and other related phenomena (^{Pitman, 1993}). Subsequently, another series of cases suggested that the course of each disorder may run a heterotypical course when comorbid, and that this may address a different, heterogeneous subtype of OCD resulting from trauma (^{Sasson et al., 2005}). Also, in one of the largest studies to date, 52% of 365 individuals with previous OCD had at least one or more earlier traumatic events (^{Cromer, Schmidt, & Murphy, 2007}). In contrast, a study found no apparent relationship between trauma, acute stress disorder, PTSD, or symptoms in patients with OCD when compared to control patients from the general population (^{Grabe et al., 2007}). Afterwards, a brief report observed that a high proportion of individuals seeking treatment for resistant OCD showcased earlier history of childhood and adulthood interpersonal violence. Of these, incestuous childhood sexual abuse, witnessing violence, and a greater frequency of experienced traumatic experiences were taken into account as putatively predictive of higher PTSD severity (^{Gershuny et al., 2008}). Ratifying the findings of this report, another study found that a history of childhood abuse was statistically more common amidst PTSD patients with pre-traumatic OCD than among their counterparts with post-traumatic OCD (^{Araújo et al., 2018}). Other researchers found in their study sample that nearly half of their participants developed OCD symptoms following exposure to combat- or terror- related trauma, and that most of those eventually met criteria for full OCD (^{Nacasch et al., 2011}). In the same vein, a case series of five Israeli veterans with no prior personal or family history of OCD or other psychiatric comorbidity who were diagnosed simultaneously with PTSD and OCD following combat trauma, described that OCD symptoms were initially related to the previous trauma, but then expanded to include other non-traumatic related triggers (^{Fostick et al., 2012}). Incidentally, another group of investigators that studied peritraumatic fear, self-focused and other-focused disgust found out that self-focused disgust was related to contamination-based OCD symptoms, while peritraumatic fear and other-focused disgust was not significantly related with this type of phenomena (^{Badour, Bown, Adams, Bunaciu, & Feldner, 2012}).

Prognostic factors (n = 6)

A small case series noted an apparent inverse relationship between symptom intensity in both conditions (when OCD symptoms lessen, symptoms of PTSD increase, and vice versa.). Likewise, the authors of this work discussed that targeting OCD (and perhaps PTSD) in isolation may hamper therapy effectiveness (^{Gershuny et al., 2003}). Moreover, another study found a significant relationship between OCD and PTSD symptoms in clinical and non-clinical samples utilizing continuous ratings instruments like the Posttraumatic Diagnostic Scale and the Obsessive-Compulsive Inventory (^{Huppert et al., 2005}). Of interest, another clinical case described a patient without earlier psychiatric comorbidities who developed PTSD, depression, and OCD after a work-related trauma. This patient scored 30 on the initial Yale Brown Obsessive-Compulsive Scale (YBOCS) and 24 on the Beck Depression Inventory. Then, he reported panic attack phenomena in trauma-related situations or when his OCD symptoms worsened. Curiously, the authors of this report commented that adequately dosed medications provided no response, including the use of fluoxetine, sertraline, citalopram, bupropion, paroxetine, and fluvoxamine (^{de Moraes, Torresan, Trench, & Torres, 2008}). Another study that compared the clinical characteristics of OCD with and without comorbid PTSD in an outpatient sample also revealed a high prevalence of OCD symptom severity for the comorbid group when the severity was measured using multiple OCD symptom dimensions (^{Shavitt et al., 2010}). Other researchers noticed that severe OCD symptoms were found in patients with a higher degree of dissociative symptoms. In this report, is was shown that YBOCS scores were significantly correlated to severity of dissociation, anxiety, depression, and traumatic phenomena (^{Semiz, Inanc, & Bezgin, 2014}). Lastly, a naturalistic, seven-year, longitudinal OCD study reported that individuals with comorbid OCD and PTSD had more severe and impairing OCD symptoms, poorer insight, lower quality of life, and greater incidences of lifetime affective and substance use disorders at the baseline assessment (^{Ojserkis et al., 2017}).

Treatment approaches (n = 3)

Although scarce, this section addresses few treatment modalities employed, or pondered, in patients with both comorbidities. Even if unclear, some studies have found that behavioral treatment of OCD (with or without pharmacological interventions) may be hampered by the presence of comorbid PTSD and may even be contraindicated, since this type of interventions have been shown to reactivate symptoms associated with the traumatic event (^{Gershuny, Baer, Jenike, Minichiello, & Wilhelm, 2002}). Some researchers have also distinguished in a case series that an integrated treatment approach to address both OCD and PTSD symptoms through a cognitive-behavioral system (cognitive restructuring to modify trauma-related beliefs paired with exposure and prevention therapy for OCD symptoms) may be effective when there is a functional connection between both entities (^{Van Kirk et al., 2018}). Lastly, a recent case study reported an apparent successful treatment approach with aripiprazole augmentation of sertraline (^{Rossi, Niolu, Siracusano, Rossi, & Di Lorenzo, 2020}).