The similarity between NDD comorbidity rates across adult and paediatric subgroups is potentially unexpected, and subsequently worthy of discussion. It is generally believed that NDD comorbidities are more prevalent in children than adults with OCD. This would be reflected in rates of current comorbidity, as opposed to our examination of lifetime comorbidity in this meta-analysis. The youngest sample (83) in this meta-analysis had a mean age of around 12 years, therefore the pooled sample had crossed the typical age of onset/presentation for ADHD and tic disorders (84). Similar lifetime rates for NDDs in children and adults with OCD suggest a neurodevelopmental continuum in the etiopathogenesis of this disorder.
