Genetic factors underlie PA frequency and stability during early childhood; they are also responsible for initial status and growth rate in PA. The contribution of shared environment is modest, and perhaps limited, as it appears only at 50 months. Future research should investigate the complex nature of these dynamic genetic factors through genetic-environment correlation (r GE) and interaction (G×E) analyses.
Few prospective studies spanning early childhood to early adolescence have examined separately the contribution of inattention and hyperactivity to academic achievement. The aim of the present study was to investigate whether the developmental trajectories of inattention and hyperactivity symptoms during early and middle childhood are independently associated with academic achievement at age 12 years. The independent associations between inattention and hyperactivity trajectories during early and middle childhood and academic performance at age 12 years were examined in a population-based longitudinal birth cohort (n = 2120). In adjusted analyses, high early childhood inattention trajectories were associated with teacher-rated academic performance in reading, writing and mathematics and with government exam score in writing. High and moderate inattention trajectories during middle childhood predicted lower performance on both teacher-rated academic performance and government exam scores in reading, writing, and mathematics. Hyperactivity was not a consistent predictor of educational outcomes. Childhood inattention symptoms rather than hyperactivity carry risk of poor educational outcomes at age 12 years. Children with high levels of inattention can be identified during the preschool years. Prevention programs supporting the development of attentional capacities and executive functions could help reduce the negative consequences of inattention.
Background: Peer victimization has been associated with long-lasting risks for mental health. Prior research suggests that stress-related systems underlying adaptation to changing environments may be at play. To date, inconsistent findings have been reported for the hypothalamic-pituitary-adrenal (HPA) axis, and its end product cortisol. This study tested whether peer victimization was associated with hair cortisol concentrations (HCC), and whether this association varied according to sex, timing, and changes in exposure. We also examined whether peer victimization differentially predicted depressive symptoms according to HCC. Methods: The sample comprised 556 adolescents (42.0%; 231 males) who provided hair for cortisol measurement at 17 years of age. Peer victimization was reported at seven occasions between the ages of 6 and 15 years. Results: Peer victimization was nonlinearly associated with HCC for boys only, whereas changes in peer victimization were related to HCC for boys and girls. Peer victimization predicted more depressive symptoms for all participants, except those with lower HCC. Conclusions: Our findings provide further support for persistent dysregulation of the HPA axis following exposure to chronic adversity, of which the expression may change according to sex and the severity of victimization.
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