Adolescents' digital nightlife: The comparative effects of day- and nighttime smartphone use on sleep quality

The smartphone occupies a substantial part of adolescents’ daily life, from the moment they wake up to, for some, well beyond their bedtime. The current study compared the impact of adolescents’ daytime, pre-bedtime, and post-bedtime smartphone use on their sleep quality. In addition, it explored the differential effects of lean-back and lean-forward smartphone apps. We collected data from 155 adolescents across 21 days using smartphone tracking (745,706 app activities) in combination with experience sampling (1,950 sleep quality assessments). We found no significant effects of daytime and pre-bedtime smartphone use on sleep quality, but a negative association of post-bedtime smartphone use with sleep quality (β = −.09). The association between smartphone use and sleep quality varied across app categories: Time spent on lean-forward apps around bedtime, such as social media apps right before (β = −.08) and game apps after bedtime (β = −.23), was associated with lower sleep quality. The use of lean-back apps (i.e., video players) was not associated with sleep quality, neither before nor after bedtime.