Interactive effect of sleep duration and physical activity on anxiety/depression in adolescents.

Although effects of sleep duration and physical activity (PA) have been demonstrated on mental health in adolescents, their interactive effect has not been studied. This cross-sectional study first examines this interactive effect on anxiety/depression in adolescents. A total of 983 Japanese students aged 12-17 were studied, using a self-report questionnaire. The interaction of sleep duration and amount of PA and their main effects on anxiety/depression, assessed using the 12-item General Health Questionnaire (GHQ-12), were investigated employing multiple regression, adjusting for grade and sex. Sleep duration and amount of PA were classified as being adequate or not, according to the duration and amount recommended by the National Sleep Foundation and World Health Organization, respectively. As a result, the interaction between sleep duration and amount of PA and their main effects were statistically significant. GHQ-12 score was significantly better in adolescents with either adequate sleep or adequate PA, not both, than those with neither adequate sleep nor adequate PA. The score, however, seemed no further improved in those with both adequate sleep and PA. The present study suggests that effects of sleep and PA on mental health need to be studied with consideration to their interaction.