Hippocampus and amygdala morphology in adults with attention-deficit hyperactivity disorder

Objective: Attention-deficit hyperactivity disorder (ADHD) in adulthood is a serious health problem with a prevalence of up to 4%. Limbic structures have been implicated in the genesis of ADHD; it has been suggested that they mediate mood and cognitive disturbances in affected individuals. Recently, a large study involving children and adolescents with ADHD reported bilateral enlargement of the hippocampus and indirect evidence of amygdala volume loss in this patient sample. We sought to test the hypothesis that, like in pediatric patients, there might be hippocampus and amygdala volume abnormalities in adult patients with ADHD. Methods: We studied 27 adult patients with ADHD and 27 group-matched healthy volunteers using a 1.5 T magnetic resonance imaging scanner. We manually obtained morphometric measurements of the regions mentioned. Results: In contrast to previous findings in children and adolescents, we found no significant differences in hippocampus and amygdala volumes among adults with and without the disorder. Conclusion: Findings of hippocampus enlargement and amygdala volume loss are not very stable across different samples of patients with ADHD. Contradictory findings may be related to the different locations of alterations along the complex circuits responsible for the different symptoms of ADHD. Further studies involving larger samples of adult patients with ADHD and using multimodal designs are needed.