Longitudinal relationships across sleep, physical activity, and mental wellbeing in early-to-mid-adolescence: a developmental cascades investigation.

Purpose: Sleep (SL), physical activity (PA), and wellbeing (WB) are three factors linked to positive development in adolescence. Despite theoretical support and some empirical evidence of developmental associations between these factors, few studies have rigorously investigated reciprocal associations over time separating between-person and within-person effects, and none have investigated all three in concert. Thus, it remains unclear how the interplay between SL, PA and WB unfolds across time within individuals. This study examines this question in the crucial early-to-mid-adolescence developmental transition.

Method: Separating between- and within-person effects, a random-intercept cross-lagged panel model was fitted to a dataset of N = 27,949 adolescents (age 12/13 at first timepoint) from Greater Manchester, England, using a three-by-three design (three annual timepoints: T1, T2, T3; three variables: SL, PA, WB).

Results: Analyses revealed gender-specific developmental cascade pathways. Specifically, we found positive reciprocal associations between SL and WB for girls (at T1→T2), whereas for boys, SL positively predicted WB (at both T1→T2 and T2→Τ3) but WB did not predict SL. We also found that WB predicted PA for boys (at T2→T3) but this finding was sensitive to model specification and yielded a smaller effect than other cross-lagged pathways.

Conclusion: Our results highlight the importance of sleep as a driver of adolescent wellbeing, and the role of gender in developmental cascade processes. Study strengths, limitations, and implications are discussed.