A Finnish eight-year study has found that higher self-reported screen time and lower amounts of unsupervised physical activity in childhood and adolescence are linked to slightly better cognitive performance in the teenage years, though researchers emphasise the effects are small and not causal.
The PANIC study followed 260 children who were aged between six and nine at recruitment in Finland, tracking them through adolescence to around 15 to 17 years old. The researchers say the long duration helps illuminate how daily movement patterns may influence brain development over time.
To capture physical activity and sedentary behaviour, the team used two methods. Participants and their parents completed questionnaires detailing organised sports, unsupervised physical activity, screen time and non-screen sedentary time such as reading or crafts. In addition, the children wore chest-mounted monitors for at least four consecutive days at each assessment, recording heart rate and movement to gauge time spent in different activity intensities and total sedentary time.
At the final eight-year follow-up, adolescents completed a computerized cognitive test battery measuring reaction times and accuracy across tasks assessing psychomotor function, attention, working memory and associative learning.
The self-reported data yielded some surprising associations. Accumulating more unsupervised physical activity over the eight years was linked to poorer working memory accuracy in adolescence. The authors noted the association was relatively weak statistically, but it presented an interesting contrast to common assumptions about exercise.
“We were also intrigued by the finding that some types of physical activity context (for example, unsupervised activity, as defined in our measures) showed a negative association with working memory,” Jalanko said. “That result should be interpreted cautiously and needs replication, because it may reflect unmeasured factors—such as what the activity is displacing (sleep, homework), or differences in social/educational context—rather than an adverse effect of activity itself.”
More self-reported screen time over the years was linked to faster reaction times in working memory tasks and better overall cognitive scores. Similarly, higher amounts of self-reported non-screen sedentary time were associated with faster reaction times, though this came at the cost of poorer accuracy on working memory tasks.
“One result that stood out was that more screen time was associated with better cognition in our models, because public discussion often assumes screen time is uniformly harmful,” Jalanko noted. “In our data, higher screen time was associated with slightly better performance on some cognitive measures at age 16. This does not mean that ‘more screen time makes teens smarter’—screen time is a broad category, and different content and contexts likely matter a lot.”
“More broadly, families shouldn’t view screen time as automatically harmful in all cases, but it’s still important to keep a healthy balance: protect sleep, make room for physical activity, and encourage screen use that involves active thinking rather than passive scrolling,” Jalanko added.
The chest-monitor data presented a different picture. Overall, cumulative device-measured physical activity and sedentary time were not related to cognitive performance in the general group. The physiological intensity of movement, recorded by heart rate and acceleration, did not show a broad link with brain function.
When the researchers separated the data by sex, distinct patterns emerged. Among boys, more self-reported organised sports related to better working memory, while more self-reported unsupervised physical activity linked to poorer working memory. For girls, higher levels of self-reported screen time were associated with better overall cognition, and objective measurements indicated that more light physical activity was linked to better working memory in girls but not in boys.
As with all research, there are caveats. Cognitive testing was conducted only at the eight-year mark, so causality cannot be established. “This was an observational longitudinal study, so we cannot conclude that screen time causes changes in cognition,” Jalanko emphasised. “In terms of practical importance, the observed associations were small—they are meaningful for understanding population patterns, but cognition is influenced by many factors (sleep, education, family environment, mental health, etc.), and screen time is only one part of that picture.”
It is possible that children with stronger cognitive skills gravitate toward certain screen activities or away from unsupervised physical play. The study’s categorisations—especially what counts as “screen time” or “sedentary time”—also shape the findings, and measurements rely on self-reporting or wearables that cannot distinguish, for example, reading from watching a movie.
The researchers stress that context likely matters. Screen time encompasses a range of activities; some may be beneficial or neutral, while others could be harmful. “So it would be a misinterpretation to take our findings as a recommendation for unlimited or purely entertainment-focused screen use,” Jalanko cautioned.
Looking ahead, the team proposes tracking physical behaviour and cognitive performance from early childhood into adulthood to map interactions across the lifespan. “A key next step is to move beyond observational associations and test causality more directly,” Jalanko said. “We are currently analysing data from our VERNA randomized cross-over study to examine how different intensities of physical activity affect cognitive performance acutely in adolescents.” He concluded that combining longitudinal and experimental approaches will better identify which relationships are likely causal and under what conditions.
The study, titled “Associations of Physical Activity and Sedentary Time From Childhood to Adolescence With Cognition in Adolescence: The PANIC Study,” was conducted by Petri Jalanko, Marja H. Leppänen, Bert Bond, Jari A. Laukkanen, Timo A. Lakka and Eero A. Haapala.
