Differentiation of depressive subtypes by insulin insensitivity in the recovered phase.

The glucose response to a standard insulin tolerance test (ITT) has been reported to be blunted in the acute phase of heterogeneous depressive disorders and to be normal in the recovered phase. We studied the glucose response to ITT in the recovered phase depression in patients who had previously been subclassified according to familial and clinical characteristics. All patients with depressive spectrum disease had an adequate glucose response to the ITT, whereas only 40% of patients with familial pure depressive disease and 56% of patients with bipolar illness had an adequate hypoglycemic response. There was also a trend toward a decrease in insulin sensitivity in patients who had been nonsuppressors to dexamethasone when depressed. These findings suggest that the glucose response to ITT may be a useful tool in differentiating among the heterogeneous depressive disorders.