Longitudinal course and risk factors for fatigue in adolescents: the mediating role of sleep disturbances.

OBJECTIVES This study (1) examines fatigue over 1 year in adolescents with chronic pain (n = 61) and depressive disorders (n = 51) compared with healthy adolescents (n = 60), (2) identifies longitudinal risk factors, and (3) tests sleep disturbances as a mediator between depression and fatigue. METHODS Adolescents completed questionnaires at baseline, 6, and 12 months. Mixed effects models examined associations between risk factors and fatigue; structural equation modeling assessed contemporaneous and longitudinal mediation. RESULTS Results revealed fatigue persisted at 1 year follow-up, with adolescents in the clinical samples experiencing greater fatigue than healthy youth at all time points (ps < .001). Age, baseline depression, and baseline sleep disturbances predicted longitudinal fatigue for the total sample (ps < .05), with variation in predictors by subgroup. Sleep quality mediated the contemporaneous effects of depression on fatigue in the clinical samples (ps < .05). CONCLUSIONS Findings underscore the longitudinal course of fatigue and suggest that improving sleep disturbances may reduce fatigue in clinical samples.