ADHD and conduct disorder: an MRI study in a community sample.

MRI studies of children with Attention-Deficit Hyperactivity Disorder (ADHD) have consistently attributed core deficits of inattention and impulsivity to frontal-striatal-cerebellar abnormalities; however, no study has investigated the neuroanatomical characteristics of children with ADHD and Conduct Disorder (CD). This study examined a community sample of 12 children with combined subtype ADHD (aged 8-12, 7 with CD) and 19 healthy controls matched for age, gender, handedness and poverty. Volume measurements, including left/right asymmetries, were quantified from MRI of the total brain, caudate and cerebellar vermis. No significant differences in total brain volume, caudate volume, asymmetry of the hemispheres or asymmetry of the caudate were found between the groups. Measurements of the left and total posterior superior and inferior lobes of the vermis, however, indicated smaller volumes for both pure ADHD and co-morbid children compared to the controls. Analysis of variance demonstrated no significant volumetric differences between the pure ADHD and co-morbid types. Prolonged exposure to methylphenidate was associated with caudate volumes. These results suggest ADHD and ADHD co-morbid with CD have similar deviant cerebellar morphology and replicate previous studies with an epidemiologically derived sample.