Scientists find out how screens affect sleep and depression in teens

New findings from Swedish scientists show: if teenagers spend too much time on their phones and computers, it worsens the quality of their sleep - and therefore increases the risk of depression. This is especially true for girls. The study is published in the journal PLOS Global Public Health.

Read more: PLOS Global Public Health (2025). DOI: 10.1371/journal.pgph.0004262

The study was conducted by experts from the Karolinska Institute in Sweden. They followed 4,810 schoolchildren aged 12 to 16 for a year. The students filled out questionnaires three times, in which they assessed their well-being, amount of sleep, symptoms of depression and how much time they spend watching screens in their free time.

What did the study show?

Increased screen time led to poorer sleep after just three months. Teenagers started going to bed later, and their sleep became lower quality and shorter. All of this disrupts the body's biological rhythms.

After a year, boys who spent a lot of time watching screens had higher levels of depressive symptoms. In girls, depression also increased - but not directly, but through sleep deterioration.

The scientists found that in girls, almost half (38% to 57%) of the link between screen time and depression was due to sleep disturbance. In boys, this link was less pronounced.

What to do about it?

Theresearchers remind us that the World Health Organisation (WHO) and Swedish authorities already recommend that teenagers limit screen time to 2-3 hours a day to improve sleep quality.

If teenagers spent less time watching screens, depression rates among them, especially among girls, could drop significantly, the study authors suggest.

The study shows that mental health problems in teenagers don't come from "nothing". They are often the result of everyday habits, such as spending hours on the phone before bedtime. It is important to recognise this in time and gently help teenagers to develop healthier daily routines.