A study involving over 21,000 Swedish twins has revealed that while teenagers who spend significant time online do report increased symptoms of depression and anxiety, shared genetics and family environment play a larger role than previously understood. The research, led by Tong Gong of the Department of Medical Epidemiology and Biostatistics at Karolinska Institutet, demonstrates that the correlation between screen time and mental health issues weakens considerably when comparing identical and fraternal twins.

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The investigation began in 2004, with parental assessments of screen time at age nine, followed by the twins answering surveys at ages 15, 18, and 24. By age 28, national health records were consulted to identify those diagnosed with depression or anxiety. The study found that heavy interactive screen use—such as gaming, chatting, and browsing—was linked to higher depression and anxiety rates, particularly in girls. For instance, teens who engaged in over six hours of interactive use on a weekday were more than three times as likely to receive a mental health diagnosis by age 28 compared to those who limited their usage to two hours or less.

However, when controlling for genetic and familial factors, the heightened risk associated with heavy screen use diminished significantly, dropping from over three times to about 65% higher. Interestingly, daily gaming reported at age nine was not linked to increased risk among twins.

The findings highlight that while screen usage correlates with worse mental health outcomes, the shared environment and genetic factors have a substantial impact. Gong noted that the surprising drop in correlation when comparing twins suggests the need for improved understanding of the context in which teens use screens.

Despite these findings, the researchers emphasized that the potential for a smaller direct effect of screens remains. They have plans for future research to explore the nature of online activities, motivations behind screen use, and how these factors contribute to mental health across different ages and sexes.

The complete study was published in the journal Nature Human Behaviour.