An Experimental Study
ResearchPosted on rand.org Apr 1, 2026Published in: Annals of Behavioral Medicine, Volume 60, Issue 1, kaag008 (2026). DOI: 10.1093/abm/kaag008
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.
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.
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.
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.
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