Participants with insomnia will initiate treatment with lemborexant 5 milligram (mg), tablet, orally as per the clinical judgment of the treating physician as part of routine clinical care. Dosage and administration of lemborexant tablet will be according to package insert and actual dosing and frequency will be decided by physician including dose escalation from initial dose of 5 mg up to 10 mg once daily. All participants will be observed prospectively for up to 24 weeks.

Lemborexant oral tablets.

The adverse events considered by the investigators to be related to treatment with lemborexant will be classified as ADRs. The incidence of somnolence, parasomnia symptoms (nightmare, abnormal dreams, exploding head syndrome etc.), narcoleptic symptoms (sleep paralysis, hypnagogic hallucination, hypnopompic hallucination and cataplexy etc.), and suicidal ideation/suicidal behavior (intentional overdose, self-injurious ideation, suicidal ideation etc.) will be determined.

Response to treatment will be assessed by the impression of general improvement consisting of "Improvement", "No change", and "Worsening". One of these ratings will be selected based on physician's impression according to participants' complaints of insomnia symptoms and will be recorded in Electronic Data Capture (EDC).