A Swedish twin study suggests that screen time and mental health are linked among young people, but that genetic and family factors may account for much of the association. The research, published on 8 October in Nature Human Behaviour, followed 21,797 twins from childhood into early adulthood.
Researchers at Karolinska Institutet examined how recreational screen habits related to symptoms of depression and anxiety. By comparing twins who spent different amounts of time using screens, they could account for genes and aspects of upbringing that the twins share.
Interactive screen time showed the strongest links
Among teenagers aged 15 and 18, longer periods spent gaming, chatting and browsing the internet were associated with higher levels of depressive and anxiety symptoms. At age 15, participants reporting more than six hours a day of interactive screen use had more symptoms than those reporting two hours or less.
In the overall sample, heavy interactive screen use at 15 was also associated with a higher likelihood of receiving a clinical diagnosis of depression or anxiety in later years. The researchers found much weaker or no corresponding links for passive activities such as watching television and videos.
What comparing twins reveals about mental health
The picture changed when the team compared twins within the same family. Most of the associations became smaller, particularly among identical twins, who share their genetic makeup and much of their home environment. After the researchers adjusted for multiple statistical tests, the associations found in the co-twin comparisons were no longer statistically significant.
That does not show that heavy screen use is harmless, nor does it rule out smaller direct effects. It suggests that studies comparing unrelated teenagers may overstate the contribution of screen time if they cannot fully account for family background. The researchers also observed a modest association in the other direction: young people with more anxiety or depressive symptoms at 15 tended to report slightly heavier interactive screen use at 18.
Why screen time alone cannot tell the whole story
The findings come with limitations. Screen use was reported by participants or their parents, and broad categories such as gaming and browsing did not capture what young people actually experienced online or why they used screens. Data collection began before smartphones and social media became central to daily life. Participation also declined in later follow-up surveys, limiting some comparisons.
Emma Frans, a researcher at Karolinska Institutet and a co-author of the study, cautioned against relying on screen-time totals alone when developing advice for families.
“Future recommendations should not focus solely on how much time children and young people spend in front of screens.”
The researchers want to examine the content of digital activities, why young people engage in them and what they replace. Their findings add nuance to Sweden’s wider efforts to encourage healthier screen habits, suggesting that the context of screen use matters alongside the number of hours spent online.
