Twin Study Reveals Complexity Behind Screen Time and Teen Mental Health

Conducted by Tong Gong and Yi Lu from Karolinska Institutet, alongside researchers from Örebro University and the University of Melbourne, the study found that while screen use correlates with mental health symptoms, the connection weakens when comparing twins raised together. This suggests that common genes and upbringing may contribute to both screen time habits and mental health issues.

The cohort began tracking these twins in 2004, with parental reports on screen use at age nine and follow-up surveys answered by the twins at ages 15, 18, and 24. Notably, a decline in participation was observed, dropping from about 16,000 at age 15 to fewer than 6,000 by age 24. Additionally, national health records were utilized to track diagnoses of depression or anxiety, as well as prescriptions for antidepressants, up to age 28.

Findings showed that as teenagers increased their screen time—particularly through gaming, chatting, and browsing—they reported more mental health symptoms. At age 15, about 24% of the twins reported more than four hours of interactive screen use on weekdays, rising to 40% on weekends. The symptoms were found to increase more sharply among girls than boys.

By age 28, teens who used interactive screens for over six hours on a weekday were over three times more likely to be diagnosed with depression or anxiety compared to those who limited their use to two hours or less. However, this statistic was derived from the broader group before accounting for familial factors. Notably, daily gaming reported at nine years old correlated with a 38% higher risk of a diagnosis by age 22.

When twins were compared directly, accounting for shared genetics and upbringing, the increased risk of depression or anxiety diagnoses dropped to about 65% higher. This effect diminished especially among identical twins, indicating that the resemblance in mood symptoms could be influenced by their shared environment and genes. Gong remarked that the significant drop was unexpected and worth further investigation.

While heavy screen use does appear to contribute to mental health risks, the researchers emphasize that simply reducing screen time may not fully address the mental health crisis. The study highlights the need for examining not just how much time is spent on screens, but also the nature of the activities and the context in which they occur.

The researchers plan to explore more about the specific online activities teenagers engage in, the motivations behind their screen use, and how these factors might evolve with age and differ by gender. The findings have been published in the journal Nature Human Behaviour.