Dexamethasone suppression test in depression: association with duration of illness

Plasma cortisol response to 1 mg dexamethasone suppression test was investigated in 37 patients with primary major depressive illness. Non-suppression of plasma cortisol was found in 14 of 37 (38%) patients. Duration of the index episode of illness was significantly shorter in the non-suppressors (11.1 +/- 9.1 weeks) than in the suppressors (29.7 +/- 25.6 weeks). The two groups were not distinguished by age, sex, polarity or severity of depressive symptoms. Eighty per cent of the non-suppressors (4/5) and 57% of the suppressors (8/14) had severe life events or major difficulties in the 6 months preceding the onset of illness, but this difference failed to reach statistical significance.