Excessive arousal has a role in the pathophysiology of major depressive disorder (MDD). Seltorexant (JNJ-42847922/MIN-202) is a selective antagonist of the human orexin-2 receptor (OX2R) that may... Show moreExcessive arousal has a role in the pathophysiology of major depressive disorder (MDD). Seltorexant (JNJ-42847922/MIN-202) is a selective antagonist of the human orexin-2 receptor (OX2R) that may normalize excessive arousal and thereby attenuate depressive symptoms. In this study, the effects of night-time arousal suppression on depressive symptoms were investigated. 47 MDD patients with a total Inventory of Depressive Symptomatology (IDS) score of >= 30 at screening were included in a randomized, double-blind, diphenhydramine-, and placebo-controlled multicentre study. Symptoms of depression were rated using the 17-item Hamilton Depression Rating Scale (HDRS 17 ). Effects on sleep were evaluated by polysomnography and by the Leeds Sleep Evaluation Questionnaire (LSEQ). To investigate the safety and tolerability of seltorexant, vital signs, suicidal ideation and adverse events were monitored. At baseline the severity of depressive symptoms correlated with sleep efficiency (SE), wake after sleep onset (WASO), duration of stage 2 sleep, and ruminations. Ten days of treatment with seltorexant (and not diphenhydramine) resulted in a significant improvement of core depressive symptoms compared to placebo; the antidepressant efficacy of seltorexant was maintained with continued treatment up to 28 days. Compared to placebo, the antidepressant efficacy of seltorexant coincided with an overall increase in (left posterior) EEG power and a relative increase in deltaand decrease in theta-, alpha- and beta power during stage 2 sleep. Treatment with seltorexant was associated with mild, self-limiting adverse drug reactions. Seltorexant affected core symptoms of depression in the absence of overt changes in the hypnogram; in contrast, diphenhydramine was not efficacious. Show less