Binge Eating Disorder (BED) group inclusion criteria:
1. Age 18-50 years, inclusive
2. Female or male
3. BMI ≥30 kg/m2
4. Current BED diagnoses by Diagnostic and Statistical Manual of Mental Disorders-5 (DSM-5) criteria confirmed by Structured Clinical Interview (SCID-5)
5. Moderate or severe BED (≥3 binge eating episodes/week in the past 14 days)
6. No current pharmacological treatment for BED, or if receiving treatment dose stable for ≥ 2 months
7. If receiving psychotherapy, intervention must be stable for ≥ 3 months and agree to continue during the study
8. Other psychiatric disorders will be permitted as long as they are not more than moderate in severity
9. Using an effective contraceptive method (participants of childbearing potential)
BED exclusion criteria:
1. Current severe comorbid psychopathology (i.e; mania, severe major depressive disorder (MDD), psychosis)
2. Current (past month) substance use disorder (caffeine and nicotine allowed)
3. Chronic use of bright light therapy (BLT) or melatonin in the past month
4. Current contraindication or history of melatonin allergy or non-tolerability;
5. Current contraindication or history of BLT non-tolerability
6. Significant risk of suicide according to Columbia-Suicide Severity Rating Scale (CSSRS) or clinical judgment, or suicidal behavior in the past year
7. Routine shift work (night work) in the past month
8. Travel across more than 1 time zone in the past two weeks
9. Current treatment with medication known to affect the circadian system or melatonin measurements, including: B-blockers, hypnotic sedatives, anticoagulants, antidiabetes drugs, oral corticosteroids, and other immunosuppressant medication
10. Current lesions or bleeding in the oral cavity, as it may alter DLMO measurements
11. Clinically significant unstable medical conditions as judged by the clinician, including: seizure or neurodegenerative disorders, thyroid conditions, autoimmune disorders, and cardiovascular disease
12. Pregnancy or breastfeeding
13. Participation in a clinical trial in the past month
14. Suspected intelligence quotient (IQ) \<80
15. Any other clinically relevant reason as judged by the clinician
Control group inclusion criteria:
1. Age 18-50 years, inclusive
2. Female or male;
3. BMI ≥30 kg/m2
4. No current or lifetime history of BED or bulimia nervosa diagnoses confirmed by SCID-5
5. No current (past month) psychiatric diagnosis according to SCID-5, including substance use disorders (caffeine and nicotine allowed)
6. No current psychiatric or psychological treatment, or if receiving treatment dose/intervention stable for ≥ 2 months
Control group exclusion criteria:
1. Clinically significant unstable medical conditions as judged by the clinician, including: seizure or neurodegenerative disorders, thyroid conditions, autoimmune disorders, and cardiovascular disease
2. Chronic treatment with BLT or melatonin in the past month
3. Routine shift work (work at night) in the past month
4. Travel across more than 1 time zone in the past two weeks
5. Significant risk of suicide according to CSSRS or clinical judgment, or suicidal behavior in the past year
6. Current treatment with medication known to affect the circadian system or melatonin measurements, including, B-blockers, hypnotic sedatives, anticoagulants, antidiabetes drugs, oral corticosteroids, and other immunosuppressant medication
7. Current lesions or bleeding in the oral cavity, as it may alter DLMO measurements
8. Pregnant or breastfeeding
9. Participation in a clinical trial in the past month
10. Suspected IQ\<80
11. Any other clinically relevant reason as judged by the clinician
