Preliminary evidence for persistent abnormalities in amygdala volumes in adolescents and young adults with bipolar disorder

Abstract

Objectives-Abnormalities in volumes of the amygdala have been reported previously in adolescents and adults with bipolar disorder (BD). Several studies have reported reduced volumes in adolescents with BD; however, both decreases and increases in volumes have been reported in adults with BD. Understanding of potential developmental contributions to these disturbances in morphology of the amygdala has been limited by the absence of longitudinal data in persons with BD. Here we use a within-subject longitudinal design to investigate whether amygdala volume abnormalities persist in adolescents and young adults with BD over a time interval of approximately 2 years.Methods-Participants included 18 adolescents and young adults: 10 participants with BD I and 8 healthy comparison participants. Amygdala volumes were measured on high-resolution magnetic resonance imaging scans acquired twice for each subject over intervals of approximately 2 years. Amygdala volumes were the dependent measures in a mixed-model statistical analysis to compare amygdala volumes between groups over time while covarying for total brain volume.Results-Amygdala volumes were significantly smaller in adolescents and young adults with BD compared with healthy participants (p = 0.018). The effect of time was not significant.Conclusions-Although the sample size is modest, this study provides preliminary evidence to support the presence of decreased amygdala volumes in adolescents and young adults with BD that persist during this developmental epoch. Keywords adolescents; amygdala; bipolar disorder; magnetic resonance imagingThe amygdala has long been implicated in the pathophysiology of mood disorders. Early observations of bipolar-type mood symptoms associated with medial temporal seizure foci prefigured the notion that abnormalities in the morphology and activity of the amygdala might contribute to the symptoms of primary bipolar disorder (BD) (1,2). Abnormal emotional (3,7,8). The divergent levels of amygdala activity detected between groups may relate to underlying differences in volume of the amygdala that have been observed in structural imaging studies. While many studies of amygdala volumes in adults with BD have reported differences between individuals with BD and HC participants, these findings have been highly variable, including both increases and decreases in volume of the amygdala in adults with BD (9-13).The few extant morphological studies of the amygdala in adolescents with BD have yielded more consistent findings than have the adult studies. Several groups have reported smaller amygdala volumes in adolescents with BD compared with HC adolescents (13-16), suggesting that smaller amygdala volumes may be present in at least a subset of individuals who manifest symptoms of BD in adolescence. Our previous cross-sectional study reported reduced amygdala volumes in both adolescents and adults with BD (13). Although inferring longitudinal trajectories from cross-sectional data such as these must be done cautiously, our findings did ...

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