Plasma ACTH levels in depression before and after recovery: relationship to the dexamethasone suppression test

Sixteen patients with major depressive disorder who were nonsuppressors on the dexamethasone suppression test (DST) on hospital admission were studied for plasma levels of adrenocorticotropic hormone (ACTH). Eight patients reverted to normal suppression with clinical recovery, while eight remained nonsuppressors. There was a significant reduction of ACTH levels in those who normalized on their DST, while ACTH levels remained high in the group that continued to be nonsuppressors. The results favored the hypothesis that dexamethasone nonsuppression in depression is mediated by high ACTH levels.