Chronobiologic parameter changes in patients with major depressive disorder and sleep disturbance treated with adjunctive brexpiprazole: An open-label, flexible-dose, exploratory substudy

•This study evaluated chronobiologic sleep parameters in major depressive disorder.•Nine depressed patients received open-label adjunctive brexpiprazole for 8 weeks.•The mean phase angle between peak cortisol and dim-light melatonin onset increased.•Change in phase angle correlated with improvement of depressive symptoms.•Phase angle may be a biomarker of antidepressant treatment response.