Screen time and physical activity habits linked to adolescent stress and depression

A new study published in JAMA Network Open suggests that higher physical activity and lower screen time from childhood through adolescence are associated with lower levels of stress and depressive symptoms by age 15. The research followed over 500 Finnish children for eight years and found that young people who engaged in more supervised exercise and spent less time on computers and mobile devices reported better mental health outcomes in their teen years. The associations were particularly strong for screen time, especially mobile device use, which was linked to higher levels of perceived stress and depression.

Mental health problems like depression and anxiety are major public health concerns among adolescents worldwide. These conditions often begin during the teenage years and are the leading cause of disability among young people. In Finland, mental health disorders are the most common reason adolescents receive sickness benefits.

Given the widespread nature of these challenges, the researchers wanted to explore which lifestyle behaviors—such as physical activity, sedentary behavior, sleep, and diet—might act as risk or protective factors for developing mental health problems.

“Mental health problems in adolescents are an increasing issue also in Finland, and we need more information about possible risk and protective factors. We know that a variety of lifestyle factors—such as physical activity, screen time, and diet—may influence mental health, but there is still little information on how these factors from childhood are related to later mental health in adolescents,” said study author Eero A. Haapala, a senior lecturer at the University of Jyväskylä.

Previous studies have shown mixed findings about the impact of physical activity and screen use on mental health. Many have relied on cross-sectional designs that capture just one point in time, rather than tracking habits over a longer period. To build a clearer picture, the researchers designed a prospective study to examine how lifestyle behaviors from childhood through adolescence might relate to stress and depression later on.

The researchers used data from the Physical Activity and Nutrition in Children (PANIC) study, which began in 2007 in Finland. The PANIC study initially included 504 children aged 6 to 9 years. Over the next eight years, researchers conducted follow-ups at two and eight years, collecting data on physical activity, screen time, diet, sleep, and mental health.

At the final follow-up, 187 adolescents (mean age around 15.8 years) had complete self-reported data on lifestyle behaviors and mental health symptoms, while 170 had valid data from wearable devices that measured activity and sleep.

Physical activity and screen time were assessed through both questionnaires and wearable accelerometers. The questionnaires captured how often participants engaged in supervised exercise (such as sports teams), unsupervised physical activity (like playing outdoors), and screen time behaviors (including time spent watching TV, using computers, or mobile devices). Diet quality was evaluated using food diaries, and a Baltic Sea Diet Score was used to rate overall diet quality. Sleep was measured through devices worn continuously for at least four days.

Mental health outcomes were assessed using the Finnish version of the Cohen Perceived Stress Scale and the Beck Depression Inventory. Researchers also recorded background factors such as body fat percentage, pubertal development, and parents’ educational levels to control for their effects in the analyses.

The researchers found that self-reported physical activity—particularly supervised exercise—was linked to lower levels of perceived stress and depressive symptoms in adolescence. On the other hand, higher total screen time, especially mobile device use, was associated with higher stress and depressive symptoms.

These associations held even after controlling for body fat and other lifestyle behaviors. For example, adolescents who reported more total screen time across the eight years had moderately higher levels of depression and stress. This was especially true for mobile device use, which had stronger links to depressive symptoms than TV or computer use.

Interestingly, device-assessed physical activity did not show the same strong relationships with mental health outcomes. In fact, light activity measured by devices was linked to higher stress and depression scores in boys. This unexpected finding could be because light activities like walking or commuting don’t provide the same psychological benefits—such as a sense of accomplishment or social interaction—as structured or vigorous physical activity.

“For parents, I would say that they should balance their kids’ behaviors between active play and screen time,” Haapala told PsyPost. “Some screen time won’t harm if other aspects of life, such as seeing friends, free play, and developing self-esteem through sports, are in balance. It is good to remember that if a kid has two hours of screen time daily, it adds up to almost one month per year—it always replaces something.”

Unexpectedly, the associations between screen time and mental health problems were generally stronger than those of physical activity. Specifically, total screen time and mobile device use showed moderate links to higher levels of depressive symptoms and perceived stress, while the associations between physical activity—especially supervised exercise—and mental health were smaller and less consistent. In fact, many of the beneficial effects of physical activity were reduced when screen time was taken into account.

“That was surprising because we still have better evidence on beneficial effects of physical activity on mental health from randomized controlled trials than we have for screen time,” Haapala said.

The study also found that boys benefited more than girls from higher levels of total and unsupervised physical activity in terms of mental health. In contrast, screen time’s negative association with mental health was consistent across sexes.

While the study had several strengths, such as using both self-reported and device-based measures and tracking behaviors over eight years, it also had limitations. The sample size at the final follow-up was relatively small, which could reduce the ability to detect more subtle effects. There was also a significant amount of missing data, which could bias results.

Another limitation was that the researchers did not assess the specific content of screen time—such as whether adolescents were using social media, playing games, or watching videos—which may have different psychological effects. The study also measured only sleep duration, not sleep quality or disturbances, which can also affect mental health.

Because the study was observational, it cannot establish cause and effect. It’s possible that adolescents with more stress or depressive symptoms may gravitate toward screens or avoid physical activity, rather than the other way around. “We just had an observational study, so cause and effect should be interpreted cautiously,” Haapala said.

To better understand causality, the research team is now applying for funding to run a full-scale randomized controlled trial. This future study will compare the effects of reducing screen time, increasing physical activity, or combining both strategies on mental health outcomes in adolescents.

The study, “Childhood Lifestyle Behaviors and Mental Health Symptoms in Adolescence,” was authored by Eero A. Haapala, Marja H. Leppänen, Silja Kosola, Kaija Appelqvist-Schmidlechner, Siiri-Liisi Kraav, Juuso J. Jussila, Tommi Tolmunen, David R. Lubans, Aino-Maija Eloranta, Ursula Schwab, and Timo A. Lakka.