Observational StudyMechanisms of Depression and Anhedonia in Adolescents: Linking Sleep to Reward- and Stress-Related Brain Function

Inclusion Criteria:

1. 14-18 years of age
2. Currently in high school
3. short and late sleep (weekday sleep duration ≤ 7 h and bedtime ≥ 22:30 (10:30 pm); n=100) or long and early sleep (weekday sleep duration > 7 hours and bedtime ≤ 22:30 (10:30 pm); n=50), indexed by the Munich Chronotype Questionnaire
4. Lifetime stressful event frequency ≥ 2 on the Stress and Adversity Inventory (STRAIN) Screener
5. Depressive symptom severity t-score greater than or equal to 45 on the Patient Reported Outcomes (PROMIS) Depression scale
6. English language fluency

Exclusion Criteria:

1. Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5) criteria for current moderate to severe alcohol/substance use disorder (≥4 symptoms);
2. Current clinician-provided diagnosis of narcolepsy or idiopathic hypersomnia;
3. Lifetime diagnosis of bipolar or schizophrenia spectrum disorder;
4. Certain medical conditions (e.g., serious neurological disorder, heart failure or serious heart trouble, history of head injury with unconsciousness > 5 minutes);
5. Conditions that are contraindicated for magnetic resonance imaging (MRI; e.g., ferrous metal in the body);
6. Positive screen for participant-reported eye disease, epilepsy, or photosensitizing medications that are contraindicated during the manipulation condition when bright light is administered (e.g., psychiatric neuroleptic drugs \[e.g., phenothiazine\], psoralen drugs, antiarrhythmic drugs \[e.g., amiodarone\], antimalarial and antirheumatic drugs, porphyrin drugs used in photodynamic treatment of skin diseases);
7. Use of melatonin if participant is not willing to discontinue use for the duration of the study.

We will schedule around (i.e., delay appointments as needed) to avoid the timeframe of the following events:

1. urgent suicide risk, defined by moderate/severe risk per Columbia Suicide Severity Rating Scale (CSSRS) and clinician determination that current risk requires immediate action;
2. travel across two or more time zones within the month prior to the overnight study visits;
3. beginning or ending a prescribed medication within 2 months of the observational study;
4. prescribed medication dose changes within the timeframe calculated as 5x the drug's half-life \[the time to reach pharmacokinetic steady-state\] before the initiation of the observational or experimental studies;
5. anticipated change in prescribed medications or medication dosing during the observational or experimental studies;
6. current symptoms of airborne infectious illness prior to laboratory visits.

Participants with positive breathalyzer screen (blood alcohol level > .02) will be rescheduled for an alternative overnight visit date.