Cross-sectional study of abnormal amygdala development in adolescents and young adults with bipolar disorder

Background: In vivo imaging studies in adult bipolarpatients have suggested enlargement of the amygdala. It is not known whether this abnormality is already present early in the illness course or whether it develops later in life. We conducted a morphometric MRI study to examine the size of specific temporal lobe structures in adolescents and young adults with bipolar disorder and healthy control subjects, as well as their relationship with age, to examine possible neurodevelopmental abnormalities. Methods: Subjects included 16 DSM-IV bipolarpatients (16 +/- 3 years) and 21 healthy controls (mean age SD = 17 +/- 4 years). Measures of amygdala, bippocampus, temporal gray matter, temporal lobe, and intracranial volumes (ICV) were obtained. Results: There was a trend to smaller left amygdala volumes inpatients (mean volumes +/- SD = 1.58 +/- .42 mL) versus control subjects (1.83 +/- .4 mL; F = 3.87, df = 1,32, p =.06). Bipolar patients did not show significant differences in right or left bippocampus, temporal lobe gray matter, temporal lobe, or right amygdala volumes (analysis of covariance, age, gender, and JCV as covariates, p >.05) compared with healthy control subjects. Furthermore, there was a direct correlation between left amygdala volumes and age (r =.50, p =.047) in patients, whereas in healthy controls there was an inverse correlation (r = -. 48, p =.03). Conclusions: The direct correlation between left amygdala volumes and age in bipolar patients, not present in healthy control subjects, may reflect abnormal developmental mechanisms in bipolar disorder,