Glucose metabolism in the amygdala in depression: Relationship to diagnostic subtype and plasma cortisol levels

In a previous positron emission tomography (PET) study of major depression, we demonstrated that cerebral blood flow was increased in the left amygdala, in unipolar depressives with familial pure depressive disease (FPDD) relative to healthy controls [J. Neurosci. 12 (1992) 3628.]. These measures were obtained from relatively low-resolution PET images using a stereotaxic method based upon skull X-ray landmarks. The current experiments aimed to replicate and extend these results using higher-resolution glucose metabolism images and magnetic resonance imaging (MRI)-based region-of-interest (ROI) analysis. The specificity of this finding to FPDD was also investigated by assessing depressed samples with bipolar disorder (BD-D) and depression spectrum disease (DSD). Finally, the relationship between amygdala metabolism and plasma cortisol levels obtained during the scanning procedure was assessed. Glucose metabolism was measured using PET and F-18-fluorodeoxyglucose ((18)FDG) in healthy control (n = 12), FPDD (n = 12), DSD (n = 9) and BD-D (n = 7) samples in the amygdala and the adjacent hippocampus. The left amygdala metabolism differed across groups (P<.001), being increased in both the FPDD and BD-D groups relative to the control group. The left amygdala metabolism was positively correlated with stressed plasma cortisol levels in both the unipolar (r =.69; P<,005) and the bipolar depressives (r = 0.68;. 1