Acute Onset of Suicidal Ideation after Starting Lemborexant in a Patient with a Mood Disorder.

A 24-year-old woman with treatment-resistant depressive symptoms and chronic insomnia developed acute, intrusive suicidal ideation with intent on day 5 after starting lemborexant 10 mg nightly. Emergency assessment did not identify intoxication, metabolic disturbance, psychosis, mania, akathisia, or other acute precipitants. Pretreatment polysomnography showed severe insomnia with a sleep efficiency of 14.5% and absent REM sleep, without sleep-disordered breathing. Lemborexant was discontinued immediately, and suicidal ideation resolved completely within 24 hours without additional pharmacological intervention. The Naranjo Adverse Drug Reaction Probability Scale yielded a score of 6, consistent with a probable adverse drug reaction. At 6-month follow-up, the patient remained free of suicidal ideation with sustained functional stability. This case adds clinically relevant documentation to pharmacovigilance concerns about potential suicidality with dual orexin receptor antagonists and supports structured suicide risk assessment and early follow-up when initiating these agents in patients with mood disorders.