Cortical structural deficits were not associated with comorbid depression or anxiety. The effect sizes of these small sub-groups with comorbid anxiety or depression indicate insufficient statistical power to address this issue with certainty. From a clinical point of view comorbid Tourette’s syndrome and attention-hyperactivity-deficit disorder are more relevant to study in children with OCD. Because of the lack of systematic clinical investigation of comorbidities we were unable to investigate this. Common comorbidities may be more aptly termed interacting variables, as they interact in complex ways. Therefore, excluding comorbid conditions will ignore complex interactions that are often integral to the disorder.
