Delayed Sleep Phase Syndrome

The goal of this study is to understand factors that contribute to delayed sleep wake phase disorder (DSWPD). The investigators will examine whether patients with DSWPD exhibit alterations in circadian rhythms and sensitivity to light compared to healthy controls. The investigators will also test a new method of predicting circadian rhythms form a blood sample.

The purpose of the study is to evaluate whether Lemborexant is more effective than placebo in shortening sleep onset latency in patients with delayed sleep phase syndrome (both type 1 and type 2). This will be tracked using sleep logs as well as actigraphy. In this 2-year study, the investigators will examine if Lemborexant administered 5-10 mg nightly taken at desired bedtime (at least 2 hours prior to self-reported sleep onset habitual time) can improve the symptoms of Delayed Sleep Phase Syndrome.