This is, to our knowledge, the largest meta-analysis of OCD comorbidity over the lifespan. Lifetime comorbid psychiatric illness is the rule rather than the exception in OCD, regardless of age. This may reflect common underpinnings across psychiatric disorders (102), overlapping phenotypes and/or sequelae of OCD pathology. In this context, information from our meta-analysis on base rates of common comorbid disorders with OCD would improve their identification and overall diagnostic efficiency (103). Our findings suggest that age, both of onset and at assessment, is a relevant factor influencing comorbidity profile and thereby, also treatment. Clinicians must screen for neurodevelopmental disorders in both children and adults, for anxiety and obsessive-compulsive related disorders in children, and for mood, substance-use, and personality disorders in adults. A high prevalence of comorbid personality disorders emphasises the need to include these in the clinical evaluation of all adults presenting with OCD. Males have a higher risk for comorbidity with NDDs, SMIs, and certain anxiety disorders. Several phenomenologically similar comorbidities such as tic disorders, OCRDs, OCPD, anorexia nervosa, and panic disorder, may be missed in individuals with a
