Whether heavy screen use itself increases the risk of mental illness, or whether young people with mental illness spend more time on screens, is a subject of debate.
Researchers at the Karolinska Institutet have followed 21,000 Swedish twins from the age of nine and can now draw some conclusions.
"We saw a connection between screen time and mental health. But when we compared twins in the same family, screen time was not linked nearly as strongly to mental health," says Emma Frans, a researcher in medical epidemiology and one of the study's authors.
Depression and anxiety
By comparing twins in the same family, where one twin used screens more than the other, the researchers were able to examine how the relationship was influenced by genetic factors and upbringing. The children were followed through adolescence and into adulthood.
The researchers also tracked symptoms of anxiety and depression, using diagnostic registers and self-reported questionnaires. Screen time was reported by the participants or their parents.
The clearest links between screen use and mental health were seen among teenagers who played games, chatted and surfed the web. Very weak or no links were found for passive activities such as watching TV.
Overall, the results, published in Nature Human Behaviour, showed that 15-year-olds who spent more than six hours a day on interactive screen activities had more symptoms of depression or anxiety than peers who spent no more than two hours a day on screens.
The influence of upbringing
But when the researchers compared twins within the same family, most of the associations weakened, especially among identical twins. This suggests that both heredity and upbringing play a role.
There is a lot of talk about screen time and mental health, and what we see is that many factors influence it. It is complex and is likely to be about both what you do on the screen and what activities screen time replaces, says Emma Frans.
The first twins to be followed were born in 1992, so their screen use differs greatly from that of younger generations. In future studies, Emma Frans hopes to examine more closely how children and young people are affected by what they do on screens.
The researchers followed more than 21,000 Swedish twins from the age of nine, through adolescence and into adulthood. The first participants in the study were born in 1992.
Data was collected through questionnaires and telephone interviews with parents and twins about screen use, environment, behaviour, and physical and mental health.
The researchers also used national registers for diagnoses, medication dispensed and mortality for some of the study participants.
The study does not capture exactly what the young people did on screens or why they used them.
The study was mainly funded by the Marianne and Marcus Wallenberg Foundation and the Swedish Brain Foundation.
Source: Nature Human Behaviour and Karolinska Institutet
