Examining the impact of total sleep duration on daily affect among short-sleeping adolescents: an experimental study

Abstract Purpose This study examined whether increasing sleep duration was associated with changes in daily affect, specifically, increases in positive affect (PA) and decreases in negative affect (NA), among short-sleeping adolescents. Methods Healthy, short-sleeping adolescents (reporting <8 h sleep on school nights based on parent and adolescent screening questionnaires, n = 41, 14-17 years) participated in 1 week of baseline monitoring, then were randomized to either sleep extension (EXT; +90 min in bed; n = 21) or habitual sleep (HAB; n = 20) for 2 weeks. Both conditions established fixed bedtime and rise-time to reduce sleep variability. Sleep duration was assessed via wrist actigraphy. Participants completed the 22-item Profile of Mood States twice daily: soon after waking and at bedtime during the 3-week protocol. Results During the initial preintervention week, average nightly sleep duration was 6.42 h (SD = 1.16). In the experimental weeks, HAB averaged 6.22 h (SD = 0.95), while EXT increased to 7.00 h (SD = 0.68; P = .002). This between-group difference represented a large effect (Hedges’ g ≈ 0.87), confirming that the manipulation increased sleep duration. Morning PA increased significantly in both conditions (P < .001). There were no significant differences in morning or evening affect between the EXT and HAB conditions. Adolescents experienced lower morning NA after nights when they slept longer, based on a secondary analysis conducted in the full sample, regardless of the experimental condition (P = .005). Further, adolescents with higher average sleep duration had lower evening PA regardless of the experimental condition (P = .03). Morning PA increased from baseline to the experimental weeks in both conditions. Unexpectedly, higher between-person total sleep duration was associated with diminished evening PA, emphasizing the nuanced role of sleep patterns in shaping affective states. Conclusions Increasing nightly sleep is feasible for short-sleeping adolescents and resulted in longer sleep duration. Although affect did not differ between groups over the short intervention period, daily associations suggest that sleep may play a role in adolescents’ emotional experiences. Longer or more intensive sleep interventions may be needed to detect group-level changes in affect.