Evaluating the Effects of Tasimelteon Vs. Placebo in Delayed Sleep-Wake Phase Disorder (DSWPD)

Inclusion Criteria:

• Ability and acceptance to provide written informed consent.

• A confirmed clinical diagnosis of Delayed Sleep-Wake Phase Disorder (DSWPD).

• Men or women between 18 - 75 years, inclusive.

• Body Mass Index (BMI) of ≥ 18 and ≤ 35 kg/m^2.

Exclusion Criteria:

• Exacerbation of an existing psychiatric condition that requires change in treatmentor intervention in the past 3 months.

• Major surgery, trauma, illness, general anesthesia, or immobility for 3 or more dayswithin the last 30 days.

• Pregnancy, recent pregnancy (within 6 weeks), or women who are breastfeeding.

• A positive test for substances of abuse.

• Current tobacco user.