Diurnal variation of plasma corticosterone in depression

Hypersecretion of cortisol is associated with depression. Because corticosterone may show greater responsiveness than cortisol to exogenous ACTH in depression and it has behavioural effects in rodents, we determined whether depression is also associated with hypersecretion of corticosterone. Both cortisol and corticosterone were significantly elevated in depression, with greatest differences from control subjects during the afternoon and evening. The ratio of corticosterone/cortisol was constant and similar throughout the day in both depressed patients and controls. We conclude that there is no disproportionate endogenous hypersecretion of corticosterone in depression.