Twin study sheds new light on screen time and mental health

“Our results suggest that the association may in some cases have been overestimated because it has not been possible to fully account for shared family factors,” says Tong Gong, research specialist at the Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, and the study’s corresponding author alongside Lu Yi, senior researcher at the same department. 

The researchers have followed over 21,000 Swedish twins from the age of nine, through their teenage years and into adulthood. The aim was to investigate how leisure-time screen use is linked to symptoms of depression and anxiety over time. By comparing twins within the same family, where one twin used screens more than the other, they were able to study how the association was influenced by shared genetic and environmental factors.

Clear links during adolescence

The clearest associations between screen use and mental health problems were observed during adolescence and for interactive screen activities such as gaming, chatting and surfing the internet. In contrast, significantly weaker or no links were observed for passive activities such as watching TV or videos.

Fifteen-year-olds who spent more than six hours a day on interactive screen activities had more symptoms of depression or anxiety and were more than twice as likely to be diagnosed with such a condition later in life, compared with their peers who spent no more than two hours a day using screens. However, when the researchers compared twins within the same family, most of these links weakened, particularly among identical twins. 

“The correlations did not disappear entirely, but they did become significantly weaker, suggesting that both genes and upbringing play an important role,” says Tong Gong.

The researchers emphasise that the results do not mean that screen time is irrelevant to mental health. Interactive screen activities during adolescence were still linked to an increased risk of mental health problems later in life, although the uncertainty increased when shared family factors were included in the analyses.

Will examine different types of activities

The study is based on self-reported data on screen use and does not capture exactly what the young people were doing on their screens or why they were using them. Furthermore, the data was collected before social media and smartphones became as integral a part of young people’s everyday lives as they are today.

The next step is to examine different types of screen-based activities in greater detail, studying their content, the motivation behind their use, problematic use and the activities that screen time replaces. In this way, the researchers hope to gain a better understanding of how these complex relationships vary across different age groups and between girls and boys.