Lifetime psychiatric comorbidities were present in 69% of the pooled sample. All comorbidities were manifold times higher than general population prevalence expected for the individual disorders (49–55, 57, 59–64, 74, 75). Overall rates were slightly (although non-significantly) higher in adult (71%) vs. paediatric (64%) subgroups, which stands to reason given that lifetime rates were being noted, and as paediatric OCD is known to persist long-term in ~40% of cases (76). Mood disorders, anxiety disorders, NDDs and OCRDs were the most common comorbidities. Bio-psycho-social commonalities across these disorders spanning genetic, temperamental (32, 33), and neuropsychological vulnerabilities (77) plausibly account for these observations. Community based surveys on adults were similar to clinic-based studies in terms of the most common comorbid disorders (depressive disorders followed by anxiety disorders), however, at much lower prevalence rates.
