1137 Effects of a Chronotherapeutic Intervention in Adolescents on Reward and Impulsivity Measures Related to Substance Use Risk

Abstract Introduction Cross-sectional and prospective data in adolescents indicate that sleep and circadian rhythm characteristics are related to substance use and related problems. Experimental rodent and human data suggest sleep deprivation and circadian misalignment alter reward sensitivity and impair impulse control. Adolescents subjected to early school start times suffer sleep loss and circadian misalignment, and thus may be at particular risk for substance use through reward- and/or impulsivity-related mechanisms. In a sample of adolescents in middle or high school, we tested whether a chronotherapeutic intervention altered reward sensitivity and/or impulsivity relative to a control condition. Methods Sixty-eight 13-15 year-old middle/high school students (34 female) completed a 2-week baseline protocol before completing a randomly-assigned 2-week chronotherapeutic intervention (n=33) or a sleep-monitoring control condition (n=35). Participants assigned to the intervention maintained a stable wake-up time, 30 minutes morning bright light (via Re-Timer glasses), 2 hours evening dim light (via blue-blocking glasses), and a 1.5-hour earlier weeknight bedtime. Sleep was assessed via actigraphy during 2-week baseline and experimental periods. Each concluded with an overnight sleep lab visit during which circadian phase was assessed with the dim light melatonin onset (DLMO), while reward and impulsivity were assessed via self-report (BIS/BAS; UPPS-P) and behavioral tasks (Balloon Analogue Risk Task BART; Cued Go/No-Go Task CGNG). Mixed models accounted for biological sex. Results The intervention advanced DLMO by 34 minutes (B=-0.57, p=0.019) and extended weeknight total sleep time by 35 minutes (B=0.58,p=0.005) relative to the control. Behavioral impulsivity (CGNG) worsened in the control condition relative to the intervention (B=0.08,p=0.023). Across both groups, advances in DLMO correlated with increases in behavioral reward motivation (BART; B=-3.18, p=0.014). Conclusion Our preliminary findings suggest that a novel chronotherapeutic intervention may alter reward sensitivity and impulsivity in complex ways. However, most of the sample had not initiated substance use, and it remains unclear whether effects would generalize to adolescents with greater substance use, or if a longer-term intervention and/or follow-up period might reveal further effects. Future studies should consider longer-term interventions in substance-using adolescents to test impact on reward and impulsivity processes as well as substance use itself. Support (if any) P50DA046346 (MPIs: McClung, Buysse; Project Director: Hasler)