The elucidation of sleep regulation is not an easy task. On one side, there is a multitude of solid yet disparate data, on the other side, the topic is tempting for engaging in wild speculation, particularly with respect to the functions of sleep. Models may exert a moderating influence by mediating between the two extremes. However, also they navigate between the risk of banality in reformulating the obvious, and the peril of fancy in losing touch with empirical reality.

This open study evaluates the effect of agomelatine, a melatonergic receptor agonist and 5-HT2C antagonist antidepressant, on sleep architecture in patients suffering from major depressive disorder. Fifteen outpatients with a baseline HAMD score ⩾20 were treated with 25 mg/d agomelatine for 42 d. Polysomographic studies were performed at baseline, day 7, day 14, and day 42. Sleep efficiency, time awake after sleep onset and the total amount of slow-wave sleep (SWS) increased at week 6. The increase of SWS was predominant during the first sleep cycle. The amount of SWS decreased throughout the first four sleep cycles from day 7 and delta ratio increased from day 14 onwards. No change in rapid eye movement (REM) latency, amount of REM or REM density was observed and agomelatine was well tolerated. In conclusion agomelatine improved sleep continuity and quality. It normalized the distribution of SWS sleep and delta power throughout the night.