Sex and gender differences in OCD: A scoping review and a two subtypes hypothesis

This scoping review explores sex and gender differences in obsessive-compulsive disorder (OCD) as reported in the literature between 2009 and 2026. A comprehensive PubMed search was conducted without restrictions, using terms related to sex, gender, and OCD. 8,394 articles were screened by two reviewers, with 1,773 assessed at the full-text level. Of these, 1,038 were included: 72 meta-analyses, 19 systematic reviews, 47 narrative reviews, 3 conceptual and integrative reviews, and 897 original reports. Original reports were categorized by focus - symptomology and burden (120), comorbidities (231), epidemiology (255), human genetics (101), altered neurocognitive and neurobiological functioning (74), treatment (86), and animal models (63) - and assessed for quality using CASP checklists. There was abundant research on sex and gender effects in OCD, but limited synthesis. Identified methodological concerns included inconsistent assessments of sex and gender, variability in OCD symptom measurement, failure to account for menstrual cycle effects, and a lack of genome-wide and full-brain imaging studies. Biases in results may arise from not accounting for gender differences in insight, help-seeking behaviors, and comorbidity. We identify critical knowledge gaps and develop hypotheses for future research, incorporating recommendations for precision medicine approaches. Investigating sex and gender differences in OCD can advance equitable mental health care by addressing the specific needs of diverse populations. Appreciating these effects offers a pathway to better understanding the complexity of OCD, fostering targeted interventions and a more nuanced approach to treatment and prevention