Relationship between family income and trajectories of adjustment in adolescence: Sleep and physical activity as moderators.

INTRODUCTION
Youth from lower-income families experience adjustment problems at higher rates than higher-income peers. While adolescents have little control over family income, they do have some agency over their sleep and physical activity, two factors that have been shown to mitigate the risk of maladjustment. To test this, sleep and physical activity were examined as moderators of the longitudinal relationship between family income (indexed by income-to-needs ratio) and trajectories of adolescent adjustment problems.


METHODS
Participants included a socioeconomically diverse community sample of 252 US youth (53% female; 33% Black, 67% White) in 2012-2015. Actigraphy-based sleep duration and quality were indexed, respectively, by minutes (sleep onset to wake excluding awakenings) and efficiency (% minutes scored as sleep from onset to wake). Physical activity and adjustment were youth-reported. Outcomes included internalizing (anxious/depressive) and rule-breaking behavior. Latent growth models estimated trajectories of adjustment across ages 16 and 18 years conditional on family income, sleep, physical activity, and their interactions.


RESULTS
Relationships between family income and change in internalizing symptoms were moderated by sleep minutes, and associations between income and change in internalizing symptoms and rule-breaking behavior were moderated conjointly by sleep efficiency and physical activity.


CONCLUSIONS
Under conditions of high-quality sleep and more physical activity, adolescents with lower income reported fewer adjustment problems. Conversely, youth with both poor sleep and low physical activity were at the highest risk for maladjustment over time. Findings enhance understanding of individual differences in trajectories of mental health associated with bioregulation, health behaviors, and the sociocultural context.