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Spending more than 3 hours a day sedentary worsens teens’ mental health

Adolescents who spend more than three hours a day engaged in sedentary behaviors – including playing video games, reading for leisure or spending a lot of time distracted by screens – have a higher risk of facing psychological distress in the future.

Published

2 years ago

February 22, 2025

ZestMag.com Staff

On the other hand, moderate screen exposure (between 60 and 119 minutes per day) invested in educational activities, such as doing homework or attending classes, was considered a “protective” factor associated with less psychological distress.

Sedentary behavior among adolescents has become a growing problem worldwide, with significant implications for the physical and mental health of the population in this age group. Several studies have shown that a lack of physical activity, especially when combined with excessive use of electronic devices, contributes to an increase in problems such as obesity and cardiovascular disease.

In addition, a growing body of research shows that the effects of a sedentary lifestyle are not limited to the physical body, but can also affect mental health, increasing feelings of anxiety and depression, for example.

The study, conducted at the Institute of Psychiatry, Psychology and Neuroscience at King’s College London in the United Kingdom, analyzed information from 3,675 adolescents who were part of the Millennium Cohort Study, a project that follows children born between 2000 and 2002 and maintains a large database.

The analysis included information on sedentary behavior collected at two points in time: when the adolescents were 14 years old and then at the age of 17. In the first phase, the participants completed a diary in which they recorded the different activities they performed every ten minutes. These activities were categorized into broader contexts: general physical activity, time spent sleeping, recreational screen time, non-screen recreational time, and educational sedentary behavior.

At age 17, the same participants reported their psychological distress using a six-question questionnaire about their feelings, using a tool known as the Kessler Scale. The questions included “how often in the past 30 days” did the participant feel nervous, hopeless, restless, depressed, anxious, and worthless. Analysis of the scores, based on the scale, indicated whether or not they were in psychological distress.

According to André de Oliveira Werneck, author of the article and doctoral student at the Center for Epidemiological Research in Nutrition and Health at the School of Public Health of the University of São Paulo (FSP-USP) in Brazil, the fact that the research was based on responses to sedentary behavior recorded in a diary is one of the differences that make the results so relevant.

Werneck explains that there are several ways to measure sedentary behavior. One of them, which is more objective, uses an accelerometer (a type of device that measures how much a person moves), but it cannot distinguish between different sedentary activities, which are very broad.

“Sedentary behavior includes a variety of activities, such as using a computer, watching television, reading, listening to music, or attending class. Most research focuses on analyzing total sitting time, but we can have positive sedentary activities, such as attending class and doing homework, for example. And there are activities that are not beneficial, such as spending too much time on the Internet or playing video games,” he explains.

A second method of measuring sedentary behavior is subjective, in which people answer a questionnaire about how much time they spend sedentary, watching TV, playing video games, working, or studying in a typical week. Nevertheless, it depends on the participant’s memory.

“Having a record of all the activities of these adolescents, formalized in a diary, provides a much more faithful result and has a more reliable accuracy of the different time periods. It’s not common to use this type of tool, precisely because it’s difficult to implement,” says the doctoral student, who carried out the study as part of a research internship funded by FAPESP.

Impact of reading

To analyze the data, the researchers adjusted for several covariates, including gender, parental education, net family income, parental psychological distress, body mass index, physical activity, total sedentary time and depressive symptoms.

After cross-checking the information, they found that the adolescents spent an average of four hours a day in educational sedentary behavior (school, homework) and about three hours a day in screen and non-screen sedentary behavior. Those who spent more than 180 minutes a day on screens for leisure were associated with greater psychological distress at age 17.

Similarly – and surprisingly – the researchers found that those who spent more than three hours a day reading for leisure (especially boys) also reported more psychological distress. According to the study, while previous research has shown that reading is associated with better mental health outcomes and other healthy behaviors, this new research suggests that excessive reading may be harmful in some cases.

One of the hypotheses to explain this finding, says Werneck, is that adolescents who spend many hours reading are “displacing” time that could be spent on activities with face-to-face or outdoor social interactions, which are protective, leading to greater isolation. In addition, it is possible that some of the reading is done on screen devices (cell phones, computers or tablets), which is also harmful – there are studies in adults that link screen reading to poorer sleep because of exposure to blue light.

“This is an unexpected finding in the study, but it’s important to emphasize that very few adolescents spend a lot of time reading for leisure. Our main finding, given the general context, is that more leisure screen time [video games] was associated with worse psychological distress, while more time in educational activities was associated with less distress,” he says.

Professor Brendon Stubbs, who supervised the study, told Agência FAPESP by email that the study revealed several worrying patterns. “We found that adolescents who spent more than three hours a day on screen-based leisure activities showed significantly greater psychological distress three years later. Video games were particularly influential, with each additional hour associated with a 3% increase in psychological distress.”

According to Stubbs, the results suggest a clear dose-response relationship between excessive recreational screen time and future mental health outcomes. “Importantly, this relationship was context-dependent, meaning that educational screen time did not show the same negative effects, highlighting that the problem is not screen use per se, but how and why screens are used.”

How to minimize the impact

Based on the findings, the researchers suggest interventions that could help minimize the negative psychological effects:

Set clear limits on screen time: Implement guidelines that limit recreational screen time to less than three hours per day, as the study results show that this is when the risks increase significantly;
Focus on context: Encourage more educational and structured screen activities rather than passive recreational screen time. The study found that educational screen time had no negative effects;
Balance activities: Promote alternative leisure activities with social interaction components, as isolated screen time can contribute to psychological distress;
Gender-specific approaches: Consider personalized interventions, as work has found gender differences in effects (e.g., girls were more associated with screen use for Internet browsing, boys for video games);
Educational support: Since moderate amounts of homework and class time have been associated with less psychological distress, ensure adequate academic engagement;
Manage and optimize screen time instead of eliminating it altogether.

Werneck emphasizes that sedentary behavior is very complex, and for adolescents, each activity and context needs to be evaluated separately. “We need to focus on interventions that not only reduce sedentary behavior but also reduce it in some specific and very long activities that are more associated with psychological distress,” he concludes.

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The look and feel of your neighborhood may affect your sleep

Those living in neighborhoods rated as having a stronger sense of safety tended to sleep longer, and that this rating appeared to be shaped by the streetscape.

Published

1 week ago

August 25, 2026

ZestMag.com Staff

Your neighborhood’s “streetscape”—the physical environment of your street—is something that you have probably never consciously thought about, despite seeing it every day. But what if the streetscape was affecting you on a subconscious level and disrupting your sleep?

This intriguing question is posed by the findings of a study led by Professor Daisuke Matsushita of the Graduate School of Human Life and Ecology at Osaka Metropolitan University. The research team used AI to analyze more than 200,000 Google Street View images to identify visual neighborhood characteristics. They then linked these characteristics to the self-reported sleep of 1,089 working adults living on the lower floors of apartments in Tokyo, who were most likely to be affected by the streetscape.

They found that those living in neighborhoods rated as having a stronger sense of safety tended to sleep longer, and that this rating appeared to be shaped by the streetscape. Generally, people slept longer in areas with lots of greenery, such as leafy trees, on the street. Similarly, high “enclosure”—meaning many tall vertical buildings and few wide-open spaces—was also associated with longer sleep and fewer insomnia symptoms.

However, the study also made a surprising finding. The researchers found that highly walkable streetscapes, such as those with more sidewalks and traffic signs, were associated with a lowered sense of safety and shortened sleep duration.

This suggests that walkability does not always represent a reassuring environment. Instead, a possible explanation is that streets with extensive pedestrian infrastructure are often busier, more crowded, and used by more strangers, which may be perceived as less safe or less relaxing than quieter residential streets.

“This study demonstrates the potential for evaluating streetscape characteristics across large geographic areas in a cost-effective manner,” Dr. Matsushita said. “Based on the technique used in this study, cities could potentially measure perceived safety, beauty, liveliness, and enclosure as well as pollution and noise.”

“We hope that opening up this new perspective creates further possibilities for designing healthier neighborhoods,” he concludes.

The findings were published in Building and Environment.

NewsMakers

Workout or nap? Either can help your sleepless brain, study finds

People who either completed 20 minutes of moderate-to-vigorous exercise or took a 90-minute nap performed about 22 per cent better on memory tests after 30 hours without sleep than those who did neither.

Published

1 week ago

August 25, 2026

ZestMag.com Staff

A short workout or a nap can help protect memory after a sleepless night, a McGill University-led study has found.

Researchers found people who either completed 20 minutes of moderate-to-vigorous exercise or took a 90-minute nap performed about 22 per cent better on memory tests after 30 hours without sleep than those who did neither. The findings, published in Proceedings of the National Academy of Sciences (PNAS), point to practical ways to counter the effects of sleep deprivation.

“Sleep loss affects nearly every aspect of how we think and function, but many people can’t simply stop what they’re doing and get more sleep,” said senior author Marc Roig, Professor in McGill’s School of Physical and Occupational Therapy. “Our findings show that even a brief bout of exercise may help preserve one of our most important cognitive abilities.”

The study involved 54 healthy young adults who stayed awake for 30 consecutive hours under lab supervision. Participants were then assigned to one of three groups: a 20-minute cycling session, a 90-minute nap or a control condition. Three days later, researchers tested their memory for images they had viewed immediately after the intervention. Those who exercised or napped remembered significantly more images than participants who did neither.

Same result, different pathways

While the memory benefits were nearly identical, brain recordings revealed that exercise and napping helped in different ways.

Napping appeared to help the brain recharge, making it easier to take in and remember new information. Exercise, by contrast, helped the brain use its remaining resources more efficiently, without making participants feel more tired.

The findings could eventually inform fatigue-management strategies in workplaces where sleep loss is common and mistakes can have serious consequences, such as health care, transportation and emergency response.

“A nap isn’t always possible in the middle of a shift,” said first author Madhura Lotlikar, a doctoral candidate in McGill’s Department of Neurology and Neurosurgery. “Exercise is accessible, inexpensive and easy to implement. That makes it a promising tool to help people stay cognitively sharp when sleep is limited.”

The researchers emphasize that exercise cannot replace sleep, but it may help people function better when getting enough rest isn’t possible.

About the study

“Protecting episodic memory after sleep loss: Similar benefits of exercise and naps via distinct neural contributions” by Madhura Lotlikar and Marc Roig et al., was published in Proceedings of the National Academy of Sciences of the United States of America.

NewsMakers

Study links coffee consumption to metabolic health and sex hormones

Despite having a similar body mass index (BMI), individuals with higher coffee consumption had lower total and visceral fat and greater skeletal muscle mass than those who consumed less coffee.

Published

3 weeks ago

August 17, 2026

ZestMag.com Staff

Coffee is one of the world’s most widely consumed beverages, and previous research has linked its consumption to a lower risk of conditions such as type 2 diabetes and cardiovascular disease. However, the biological mechanisms behind these benefits remain unclear. A new Finnish study links habitual coffee consumption to healthier body composition and metabolic markers, while revealing distinct associations with sex hormones in men and women.

The study, conducted at the University of Oulu, analysed data from 2,264 participants aged 46 in the Northern Finland Birth Cohort 1966. Researchers examined how habitual coffee consumption was associated with circulating metabolites, cardiometabolic risk markers and sex hormones.

Despite having a similar body mass index (BMI), individuals with higher coffee consumption had lower total and visceral fat and greater skeletal muscle mass than those who consumed less coffee.

In both men and women, higher coffee consumption was correlated with lower circulating levels of branched-chain amino acids, biomarkers that have previously been linked to insulin resistance and an increased risk of type 2 diabetes when chronically elevated.

The strongest sex-specific associations were observed in men. Higher coffee consumption was linked to a more favourable glucose–insulin profile, higher concentrations of total and bioavailable testosterone, and increased levels of sex hormone-binding globulin (SHBG). At the same time, free testosterone and the free androgen index were modestly lower. In women, hormonal associations were more limited and were primarily characterised by higher SHBG and lower measures of free androgens.

“Coffee is consumed by millions of people every day, yet we still know surprisingly little about how it relates to our metabolism and hormones. What stood out in our findings was a distinct hormonal signature that didn’t disappear even after we took into account BMI and lifestyle factors, with several of these associations differing between men and women,” says Luca Verroest, lead author of the study and Doctoral Researcher at the University of Oulu.

The results suggest that hormonal pathways may partly explain the relationship between coffee consumption and metabolic health. However, as this was an observational study, the findings demonstrate associations rather than cause-and-effect relationships.

The study is particularly relevant in Finland, one of the world’s highest coffee-consuming countries, where annual consumption averages around 11.8 kilograms per person.

The researchers say the findings provide a foundation for future studies aimed at determining whether coffee itself drives these biological changes and identifying the compounds responsible. These questions are currently being investigated in animal models, with the long-term goal of progressing to human intervention studies. Further research will be needed before the findings could inform dietary recommendations.

The study, Associations of habitual coffee intake with testosterone and cardiometabolic markers: the Northern Finland Birth Cohort 1966 study, has been published in the European Journal of Nutrition.