This is the first systematic review and meta-analysis to examine comorbid disorders across the lifespan in individuals with OCD. The meta-analysed studies were clinic-based and reported original findings on individuals with OCD, evaluated using standardised diagnostic interviews/instruments. We chose to report lifetime comorbidities in this paper, since these were reported in the largest number of studies. We grouped the studies into adult and paediatric subgroups to examine comorbidity rates from a lifespan perspective. Meta-analyses for individual comorbidities had high heterogeneity (I2 80–98). High heterogeneity may reflect variations in demographic (mean age, gender distribution), socio-cultural (country of origin), and clinical (age of onset of OCD, illness severity) characteristics, besides differences in research methods (study design, recruitment source, decision-making processes, measurement errors, recall biases in reporting lifetime comorbidity etc.). Interestingly, heterogeneity was statistically non-significant for ASD, bulimia nervosa and anti-social personality disorder (ASPD). Based on the GRADE criteria (risk of bias, inconsistency, imprecision and indirectness, and publication bias) we report a moderate to high confidence in the presented pooled estimates.
