Subtle differences exist in ADHD, ASD, OCD across age groups

There appear to be robust but subtle differences among attention-deficit hyperactivity disorder (ADHD), autism spectrum disorder (ASD), and obsessive-compulsive disorder (OCD) across different age groups, suggests a study.

“ADHD-specific intracranial volume and hippocampal differences in children and adolescents, and ASD-specific cortical thickness differences in the frontal cortex in adults, support previous work emphasizing structural brain differences in these disorders,” the authors said.

Shared differences were not observed among all three disorders, while shared differences between any two disorders failed to survive correction for multiple comparisons. Children with ADHD had smaller hippocampal volumes compared with those with OCD, which was possibly driven by IQ. In addition, children and adolescents with ADHD had smaller intracranial volume than control participants and those with OCD or ASD.

Frontal cortices were thicker among adults with ASD compared with controls and other clinical groups. Of note, OCD-specific differences across different age groups and surface area differences among all disorders in childhood and adulthood were not observed.

This study analysed structural T₁-weighted whole-brain MRI data from healthy control participants (n=5,827) and from patients with ADHD (n=2,271), ASD (n=1,777), and OCD (n=2,323) from 151 cohorts worldwide using standardized processing protocols.

Pooling measures extracted from each cohort, the authors assessed subcortical volume, cortical thickness, and cortical surface area differences within a mega-analytical framework. They carried out analyses separately for children, adolescence, and adults using linear mixed models adjusting for age, sex, and site (and intracranial volume for subcortical and surface area measures).

“ADHD, ASD, and OCD are common neurodevelopmental disorders that frequently co-occur,” the authors noted.