In depression, changes in EEG sleep measures are well documented findings. However, the predictive value of these alterations for treatment and long-term course of depression still warrants clarification. Therefore, we examined whether the previous course of depression, treatment response during antidepressant therapy, and the long-term outcome in follow-up are associated with sleep regulation. Since the hypothalamic-pituitary-adrenocortical (HPA) system may play a crucial role in depression's neurobiology, we evaluated HPA system function as well.

15 patients (4 men, 11 women; age 43–59) with depression were enrolled in the study. HPA system assessment using the combined DEX/CRH test and sleep EEG studies were conducted at baseline, after a 6 week antidepressant treatment period (trimipramine), and at follow-up, i.e., after 2-10 years.

The previous clinical course, i.e., the number of episodes until baseline, correlated significantly with EEG sleep measures i.e. sleep continuity values, slow wave sleep (SWS) and REM latency.

During treatment sleep continuity values improved and the correlation with the previous long-term course disappeared. The correlation with SWS persisted. The only sleep EEG marker at baseline predictive for treatment response was REM latency.

In the prospective long-term outcome SWS and REM density variables were related to the occurrence of recurrences. These sleep EEG markers correlated closely with HPA system regulation.

The long-term outcome of depression is related to the sleep EEG pattern: SWS and REM density measures may reflect predictive markers for the long-term course. These markers are associated with HPA system regulation.