Orexin Antagonism for Suicide Risk: A Proof-of-Concept Clinical Trial

Inclusion Criteria: * Veteran * At least 18 years of age (up to 70 years) * Primary diagnosis of Major Depressive Disorder as determined by the study psychiatrist and confirmed by the Mini-International Neuropsychiatric Interview (MINI) * Lifetime suicide attempt history and suicidal ideation at baseline as determined by a score ≥2 on the Columbia-Suicide Severity Rating Scale (C-SSRS) Exclusion Criteria: * Clinically significant medical or neurological condition * Current use of strong CYP3A live enzymes or moderate CYP3A inhibitors or strong CYP3A inducers * Current use of digoxin * Currently pregnant, not using contraception, nursing, or trying to become pregnant * Active substance use disorder in the last six months, disorder, or current or past psychotic disorder, bipolar disorder, or obsessive-compulsive disorder * Severe traumatic brain injury * Imminent suicidal or homicidal risk * Free of unstable medical conditions or any contraindication to suvorexant (per FDA prescribing label) as determined by patient interview and review of available medical records.