OBJECTIVES: Sleep and internalizing problems escalate during adolescence and can negatively impact long-term health. However, the directionality of this risk-relationship remains poorly understood within a developmental context. The current study aimed to determine the directionality of this relationship in adolescents with no history of psychiatric disorder and whether sex at birth played a role in this relationship. METHODS: We used data from the Adolescent Brain Cognitive Development, an ongoing multisite longitudinal US study, that covered four waves (W1:9-11 years
W2:10-12 years
W3:11-13 years
W4:12-14 years). Analyses included 3,128 youth (50.99%girls) with no past or current psychiatric disorders at W1. The Sleep Disturbance Scale for Children and the Child Behavior Checklist were used to measure sleep and internalizing problems. Cross-lagged panel models were used to evaluate the cross-lagged relationships across waves. RESULTS: The sleep-internalizing cross-lagged relationship was unidirectional, with medium-large effect sizes: greater total sleep problems were associated with more severe internalizing problems at later waves (W2➔W3, coefficient = 0.052, CONCLUSIONS: Sleep-internalizing relationships change across adolescence, becoming significant and more specific from early to mid-adolescence. Sleep interventions delivered in early adolescence, to girls in particular, may have a positive short and long-term impact on internalizing outcomes.