Objective: To examine brain-behavior relationships in attention deficit hyperactivity disorder (ADHD), the authors obtained magnetic resonance imaging (MRI) scans of monozygotic twins discordant for ADHD.
Method: National recruitment was followed by in-person assessment. MRI scans were measured algorithmically for nine pairs of monozygotic twins discordant for ADHD.
Results: The affected twins had significantly smaller caudate volumes (mean difference=-0.56 ml, CI=-0.92 to -0.21) than their unaffected co-twins.
Conclusions: These results provide further support for striatal models of ADHD pathophysiology.