Teenagers who own smartphones spend more time online—including during the night, which may affect their sleep. A new University of Basel study on more than 300 students reports that teenagers’ digital media use during the night is associated with an increased risk of sleep problems and depressive symptoms. The findings have been published in the Journal of Youth and Adolescence.

While introduced only around 2007, most teenagers nowadays own smartphones. Due to wireless Internet connections and cheap flat rates, teenagers with smartphones spend more time online and communicate with their peers for less money—for example, via WhatsApp—which has changed their digital media use pattern profoundly.

A study by the University of Basel examined differences in digital media use between teenagers with smartphones and their peers with conventional mobile phones; 162 female and 200 male students from northwestern Switzerland aged 12 to 17 participated in the study. The results show that during weekdays teenagers with smartphones spent more time on the Internet than their peers with conventional mobile phones; on average, 2 hours compared to 1 hour. In addition, they wrote more text messages daily; on average, 85 messages compared to seven messages.

A particularly noticeable difference was found for the time when the teenagers were in their beds at night: Only 17% of smartphone owners switched their devices off or put them on silent during the night compared to 47% of the teenagers with conventional mobile phones. Moreover, teenagers with smartphones indicated they were watching videos, were online, and were texting with friends more often during the night than their counterparts with conventional mobile phones. Most importantly, teenagers who used digital media at night had an increased risk for poor sleep and depressive symptoms. Experts thus recommend that teenagers who suffer from sleep disorders or severe daytime tiredness switch their digital media devices off at least 1 hour before bedtime.