This is a multicenter, double-blind, randomized study to evaluate the efficacy and safety of a daily single oral dose of tasimelteon and matching placebo in male and female pediatric participants with insomnia disorder.

Inclusion Criteria:

• Ability and acceptance to provide written informed consent of the participant or legal guardian (and assent as required).
• Confirmed clinical diagnosis of insomnia disorder
• Males and Females between 2 and 17 years, inclusive.
• The sleep disturbance must not be a result of another medication.

Exclusion Criteria:

• Inability to dose daily with tasimelteon or previous intolerance to tasimelteon.
• Indication of impaired liver function.
• Pregnant or lactating females.
• A positive test for drugs of abuse.