Examining the Role of the Orexin System in Sleep and Stress in Persons With Opioid Use Disorder

Inclusion Criteria: * Between the ages of 21-65, inclusive. * Past 30-day sleep disturbance as evidenced by a Pittsburgh Sleep Quality Index Total Score \>5. * Enrolled in either outpatient methadone-maintenance, buprenorphine-maintenance, or XR-NTX treatment for OUD. * Willingness to be maintained on a protocolized dose starting between 60-130mg methadone or 380mg XR-NTX for the duration of the study. * At least two weeks of continuous abstinence from illicit opioids as evidenced by self-report and urine drug screens collected as part of routine care. * Willing to comply with the study protocol, which will include weekly study visits, daily actigraphy and ecological momentary assessments. * Use of birth control throughout study. * Have no clinically significant chronic medical disorders or conditions that are judged by the investigators to prevent participation. Exclusion Criteria: * Serious mental illnesses that are unstable and could affect study participation (thought disorders, hallucinations, delusions, thoughts of harm to self/others). * Current moderate to severe substance use disorder other than OUD. * Current illicit stimulant use, including cocaine and methamphetamine. * Pregnant or breast feeding. * Have a known allergy to the study medications. * Past 30-day prescribed use of suvorexant. * Current use of a benzodiazepine or other schedule IV medication for insomnia. * Use of Cytochrome P450 3A inhibitors. * Current narcolepsy, sleep paralysis, or restless leg syndrome as assessed by medical history * Apnea-hypopnea index \> 30. * Use of glucocorticoid medications and any medication that would alter the hypothalamic-pituitary-adrenal axis. * Past 30-day suicidal behavior as assessed by the Columbia Suicide Severity Rating Scale (C-SSRS). * Have circumstances that would interfere with study participation (e.g., impending jail; severe clinical issues).