Inclusion Criteria:

• 1. Diagnosis of PTSD via American Psychiatric Association PTSD diagnostic criteria in the fifth edition of its Diagnostic and Statistical Manual of Mental Disorders (DSM-5).
• 2. Self-report having repetitive nightmares contributing to disrupted sleep;
• 3. Age 22 years (rationale is because the device has only been used in adults in 22 years and older);
• 4. Resting blood pressure (BP, \<160/100 mmHg);
• 5. Fasted glucose \<126 mg/dL;
• 6. Poor overall sleep quality as indicated by a Pittsburgh Sleep Quality Index (PSQI) score 6 or higher;
• 7. Epworth Sleepiness Scale (ESS): Question #8 score above "0" will prompt an additional question: Do you drive ("get behind the wheel") when you are drowsy? The answer must be "No" to be enrolled in the study due to safety concerns;
• 8. Wireless Internet and two power outlets in sleeping location;
• 9. Willingness not to use any other application which collects heart rate data on the phone and watch that is used for NightWare;

Exclusion Criteria:

• 1. Unstable medical condition (e.g., uncontrolled hypertension or active CVD or cancer);
• 2. Active infection (note, anyone with an active infection would become eligible once the infection has ended);
• 3. Thyroid dysfunction, defined as an ultrasensitive TSH \<0.5 or \>5.0 mU/L; volunteers with abnormal TSH values will be re-considered for participation in the study after follow-up evaluation by the PCP with initiation or adjustment of thyroid hormone replacement; or other problems that would interfere with participation in the study;
• 4. Use of insulin or sulfonylureas
• 5. Pregnancy or currently breast feeding;
• 6. Current history (past 3 months) of substance (excluding marijuana) or alcohol abuse per the SCID-5. Adults with past substance or alcohol use disorders will be allowed to participate;
• 7. Participants will be excluded if they report elevated acute risk for suicidal self-directed violence warranting immediate hospitalization (e.g., suicidal ideation with intent, evaluated by the Columbia-Suicide Severity Rating Scale \[C-SSRS\]).
• 8. Shift workers (due to circadian rhythm disruption);
• 9. Diagnosis of active disorder of arousal from non-rapid eye movement sleep, rapid eye movement sleep behavior disorder, or narcolepsy;
• 10. Nocturia that causes awakening from sleep;
• 11. Known sleep walking or acting out dreams (contraindication to NW use);
• 12. Diagnosis or suspicion of dementia;
• 13. Seizure disorder
• 14. Participants experiencing severe cognitive impairment or current psychiatric symptoms of such severity that would preclude participation (e.g., active psychosis, imminently suicidal)