Amygdala Volume Analysis in Female Twins with Major Depression

Background Previous research examining the amygdala volumes in major depressive disorder (MDD) has found conflicting evidence for association. Furthermore, few of these studies have examined differences in individuals with an onset during childhood or adolescence. This study examined amygdala volume and its potential association with early onset major depression. Methods A community-based sample of 47 right-handed young adult female monozygotic and dizygotic twin pairs was examined. For 29 twin pairs, one twin per pair had a lifetime history of MDD, while 18 age-matched control twin pairs had no lifetime history of MDD or other Axis I disorder. Core, noncore, and total amygdala volumes were estimated based on a combination of manual tracing, automated segmentation, and expert rater regional boundary definitions. Results No significant differences were found in amygdala volumes between depressed, high-risk, or control subjects. However, analyses comparing control monozygotic twins to randomly created control subject pairs suggest that there are familial, perhaps genetic, influences on core and total amygdala volumes. Conclusions Findings suggest that although there were no significant differences in amygdala volumes between groups, familial factors influence amygdala volumes. Discrepancies between studies measuring amygdala volume in MDD may be due to differences in amygdala boundary definitions.