Heterogeneity was considerable, and statistically significant, across comorbidities except for ASD, Bulimia nervosa and ASPD. As discussed, this may be due to variations in demographic, socio-cultural, clinical characteristics and study methods. With sub-group analysis for adult, vs. paediatric, studies, we have accounted for some of these variables. Our selection criteria required a minimum sample size of 100 OCD patients. Our interest was to detect comorbidities at a low rate of 1%. The included studies however varied in the sample sizes. Only one study had a sample size of 100. A majority (49.5%) of the studies had a sample size between 101 and 200, another 23.1% had a sample size of 201–300. Inconsistency may have impacted the results of the meta-analysis.
