Changes to sleep-wake behaviors are associated with trajectories of pubertal timing and tempo of secondary sex characteristics.

We examined relations between sleep-wake behaviors and pubertal development from age 8.5 through 15.5 years in a US-based sample of 488 boys (75% White) and 478 girls (78% White). Applying conditional nonlinear growth models to 7-waves of longitudinal data, we examined how sleep-wake behaviors are related to individual differences in the developmental timing and tempo of secondary sex characteristics. For girls, results supported the hypothesis that circadian changes in bedtimes, wake times, sleep duration, and eveningness preference were uniquely related to development of discrete aspects of secondary sex characteristics. For boys, the hypothesis was generally not supported. Different endocrine systems related to discrete secondary sex characteristics may be responsible for more relations between sleep and pubic hair development than for breast or genital development. Further research into associations between adrenarche and sleep during puberty may help researchers understand more about the origins and timing of adolescent sleep changes.

Sleep, Affect, and Social Competence from Preschool to Preadolescence: Distinct Pathways to Emotional and Social Adjustment for Boys and for Girls.

Using a normative sample of 1,057 children studied across 4 waves over 6 years with multiple informants, we investigated transactional relations for sleep problems, anxious-depressed symptoms, and social functioning from preschool to preadolescence, assessing cumulative effects on children's emotional and social adjustment. To examine sex differences in the developmental processes, we conducted separate analyses for boys and girls. For both boys and girls, longitudinal cross-lagged panel analyses showed that preschool sleep problems directly predicted anxious-depressed symptoms 2 years later; indirect effects continued into preadolescence. For girls, early and later sleep problems directly or indirectly predicted a wide variety of preadolescent emotional and social adjustment domains (e.g., depressive symptoms, school competence, emotion regulation, risk-taking behaviors). For boys, social competence played a more important role than sleep problems in predicting preadolescent adjustment. Among the first set of findings that demonstrate longitudinal relations between sleep problems and social functioning in middle childhood and preadolescence, these results support Dahl's and Walker's neurological models of sleep and emotional functioning. We discuss these findings in light of relations between sleep and affect during pre-pubertal development and discuss differential findings for boys and girls.