Associations between sleep, daily smartphone use, and negative affect in U.S. adolescents

Prior research has focused on how smartphone use affects sleep, with less attention to how prior night’s sleep is associated with next-day smartphone use, or moderates the link between smartphone use and negative affect. To address these gaps, 71 adolescents (ages 15–18 years) completed ecological momentary assessments (EMAs) three times a day for 14 days. Each morning EMA included reports on prior night’s sleep quality, and all three EMAs assessed depressed and anxious affect. Adolescents wore Fitbits to track objective sleep metrics and uploaded objective smartphone use data daily. We tested whether prior night’s sleep related to greater smartphone screen time the next day, and whether prior night’s sleep moderated links between next-day smartphone screen time and negative affect (depressed, anxious). Adolescents who slept less, on average, logged more smartphone screen time overall (between-person), and on nights when adolescents reported poorer sleep quality than usual, they logged more smartphone screen time the following day (within-person). Adolescents who logged greater smartphone screen time than their own average in a given day reported greater depressed affect, and the association was strengthened by prior night’s self-reported sleep quality. Findings highlight the importance of sleep in understanding associations between smartphone use and affect during adolescence.