The study’s central innovation lies in its co-twin comparison design. Rather than simply comparing unrelated individuals, the researchers examined pairs of twins raised in the same household where one twin used screens considerably more than the other. Because identical twins share essentially all of their genes and both identical and fraternal twins share much of their family environment, differences in mental health outcomes between twins within the same pair cannot easily be attributed to those shared factors. When the researchers applied this within-family comparison, most of the observed links between screen use and mental health problems weakened considerably, particularly among identical twins, a pattern that points strongly toward genetic and environmental influences shared within families.

The clearest associations in the conventional, between-family analyses emerged during adolescence and for interactive screen activities such as gaming, chatting and surfing the internet. In contrast, the links for passive activities such as watching television or videos were significantly weaker or absent altogether. This distinction between active and passive engagement is one of the study’s most striking findings, and it complicates the simple picture of screen time as a uniform risk factor. Fifteen-year-olds who spent more than six hours a day on interactive screen activities showed 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 peers who spent no more than two hours a day using screens.

Those headline numbers, however, tell only part of the story. When the researchers compared twins within the same family, the strength of these associations dropped markedly. The correlations did not disappear entirely, but they became significantly weaker, suggesting that both genes and upbringing play an important role in shaping the apparent relationship. According to Tong Gong, research specialist at the Department of Medical Epidemiology and Biostatistics at Karolinska Institutet and the study’s corresponding author alongside senior researcher Lu Yi, the results indicate that the association may in some cases have been overestimated because it has not been possible to fully account for shared family factors in earlier research.

The implications of this methodological insight extend well beyond the specific question of screens. Much of the existing literature on digital technology and youth mental health relies on observational comparisons between unrelated individuals, which are vulnerable to confounding by any factor that differs across families. Genetic predispositions to both heavy screen use and internalising problems, parenting styles, socioeconomic conditions and household routines could all contribute to a spurious association. Twin designs, by holding these shared influences constant, provide a natural experiment that can separate within-person effects from between-family differences. The attenuation observed in this study, especially among monozygotic pairs, suggests that a meaningful share of the reported screen-mental health connection in the broader literature may reflect such confounding.

At the same time, the researchers are careful to emphasise that the findings do not mean 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 around the estimates increased when shared family factors were included in the analyses. In other words, the data cannot rule out a genuine effect of heavy interactive use; they simply show that the effect, if it exists, is smaller and harder to detect than raw population-level comparisons imply. For a field that has produced widely varying estimates of harm, this nuance matters. It shifts the scientific conversation from whether screens are good or bad toward a more precise question of which activities, in which contexts, and for which individuals, may carry risk.

The study also carries important limitations that the authors acknowledge. It is based on self-reported data on screen use, which does not capture exactly what young people were doing on their screens or why they were using them. Self-reports of media habits are known to be imperfect, and the coarse categories used in the study cannot distinguish, for example, between social gaming with friends and solitary late-night scrolling. Furthermore, the data were collected before social media and smartphones became as integral a part of young people’s everyday lives as they are today, raising questions about how the findings generalise to a generation for whom mobile, algorithmically curated content is the default mode of engagement.

The research team, which included collaborators from Sweden, Norway, Denmark, Germany and Australia, plans to address these gaps in the next phase of work. The researchers intend to examine different types of screen-based activities in greater detail, studying their content, the motivation behind their use, problematic use patterns, and the activities that screen time replaces. By mapping these dimensions, they hope to gain a better understanding of how the complex relationships between digital media and well-being vary across different age groups and between girls and boys. Emma Frans, senior research specialist at the Department of Medical Epidemiology and Biostatistics at Karolinska Institutet and co-author of the study, argues that future recommendations should not focus solely on how much time children and young people spend in front of screens. To be able to give good advice, she notes, we also need to understand what they are doing on their screens, why they are doing it, and which individual and family-related factors may affect their well-being.

For parents, educators and policymakers, the study offers a measured rather than alarmist message. Simple time-based screen limits, the findings suggest, may be a blunt instrument if the true drivers of risk lie in the nature of the activity, the motivation behind it, or pre-existing vulnerabilities that screens merely reflect. A teenager who games intensively may be doing so for reasons that also elevate their risk of depression, and reducing screen hours alone may not address the underlying issue. At the same time, the persistence of some association even within twin pairs leaves open the possibility that heavy interactive use contributes directly to poorer mental health, particularly during the sensitive adolescent period.

The study, titled Recreational Screen Use and Internalising Problems from Preadolescence to Young Adulthood in a Longitudinal Twin Cohort with Co-Twin Comparison, was primarily funded by the Marianne and Marcus Wallenberg Foundation and the Swedish Brain Foundation. The authors note that one co-author, Henrik Larsson, has received research grants, honoraria and consultancy fees from pharmaceutical companies outside the scope of this study, while the other researchers declare no conflicts of interest. As debates over youth mental health and digital technology continue to intensify worldwide, this large-scale twin analysis adds a crucial layer of methodological rigour, reminding researchers and the public alike that correlation between screen time and psychological distress may say as much about families and genes as it does about screens themselves.

Subject of Research: The relationship between recreational screen use and internalising mental health problems in young people examined through a longitudinal twin cohort study

Article Title: Twin study sheds new light on screen time and mental health

Article References: Twin study sheds new light on screen time and mental health. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: screen time, mental health, twin study, adolescence, depression, anxiety, genetics, Karolinska Institutet, Nature Human Behaviour, gaming, longitudinal study, youth well-being

A brief questionnaire designed to capture whether adolescents feel accepted, supported and safe at school has received a substantial psychometric overhaul. In a study of 621 Portuguese teenagers, researchers found that the widely used five-item School Connectedness Scale performed better after one question was removed, producing a four-item version with strong statistical properties and consistent performance across male and female students. The revised scale was also linked to higher quality of life, stronger mental well-being and a greater sense of social safety. The findings suggest that a carefully calibrated measure of school connectedness could give researchers and educators a faster way to identify how students experience their school environment—and how those experiences relate to mental health.

School connectedness is more than simply liking school or attending classes regularly. It refers to the degree to which students feel that they belong, are respected and supported, and have meaningful relationships within the school community. Adolescence is a period when social relationships become particularly important, as young people increasingly orient their attention toward peers and wider social groups. School is often the main setting where those relationships develop. When students feel integrated into that environment, previous research has associated connectedness with stronger engagement, better academic adjustment, greater life satisfaction and lower levels of risky behavior. Yet the scientific measurement of the concept remains complicated because terms such as belonging, attachment, bonding, engagement, school climate and teacher support are sometimes used interchangeably.

The new study, published in School Mental Health, focused on the five-item version of the School Connectedness Scale originally derived from the National Longitudinal Study of Adolescent Health. The researchers recruited 621 adolescents aged 11 to 18 from public schools across northern, central and southern Portugal. The sample included 315 males and 306 females, with a mean age of 13.53 years, and most participants were enrolled in the seventh through ninth grades. Students completed anonymous online questionnaires during school hours, with the participation of researchers or clinical psychologists. Written consent was obtained from the adolescents and, where required, their parents or legal guardians.

The participants answered questions assessing school connectedness alongside measures of social safeness, positive mental health, anxiety, depression and quality of life. The connectedness scale uses a five-point response format, from strong disagreement to strong agreement, producing scores that indicate the strength of a student’s perceived relationship with school. The other instruments were also structured self-report measures. Positive mental health was assessed across emotional, social and psychological well-being; anxiety and depression scales measured symptom severity and interference with daily functioning; and the KIDSCREEN-10 assessed perceived health-related quality of life across family, peer and school settings. The researchers reported good internal reliability for these measures in their Portuguese adolescent sample.

To test whether the scale measured a single underlying construct, the team used confirmatory factor analysis, a statistical method that examines how well observed answers fit a proposed latent structure. In this case, the proposed structure was a single school-connectedness factor. The original five-item model did not fit the data well: its root mean square error of approximation, or RMSEA, was 0.089, above the level generally considered acceptable. Statistical modification indices suggested that some items shared unexplained variance, particularly questions about teacher fairness and school safety. Allowing certain residual errors to correlate improved the model, but one question continued to perform poorly.

That problematic question was “The teachers at this school treat students fairly.” Its factor loading—the strength of its relationship with the underlying connectedness factor—was below 0.50 in the full sample and in both sex groups. Its corrected item-total correlation was also the lowest, at 0.39, meaning that answers to the question were less closely aligned with students’ overall connectedness scores than were the other items. The researchers argue that the item may be measuring a different psychological target. The remaining questions focus on students’ own feelings, while the teacher-fairness question asks them to make a broader judgment about how teachers treat students collectively. It also shifts from a personal perspective, such as “I feel,” to an external evaluation of the school’s staff.

Removing the question produced a much stronger one-factor model. The revised four-item scale achieved an RMSEA of 0.046, and all remaining factor loadings exceeded 0.50. Internal consistency, assessed using both Cronbach’s alpha and McDonald’s omega, was generally between 0.80 and 0.85 across the full sample and the male and female subgroups. The researchers also tested measurement invariance, a crucial step when comparing groups. Configural invariance indicated that the same general factor structure applied to both groups; metric invariance showed that the items related to the factor in comparable ways; and scalar invariance indicated that score comparisons were meaningful because item intercepts were equivalent. In practical terms, the four-item scale appeared to measure the same construct in males and females.

The analysis nevertheless uncovered a difference in average connectedness scores. Male participants reported higher school connectedness than female participants, with mean scores of 15.46 and 14.49, respectively. The difference was statistically significant and had a small-to-medium effect size, with Cohen’s d equal to 0.32. The authors stress that research on sex differences in school connectedness has produced mixed findings, with some studies reporting higher connectedness among females, some finding no difference and others, particularly in certain cultural settings, observing higher scores among males. The result should therefore not be interpreted as a universal pattern. It may reflect differences in peer relationships, perceived school safety, teacher interactions or the social context of Portuguese public schools.

The strongest evidence for the revised scale came from its relationships with other aspects of adolescent well-being. Higher connectedness scores were associated with greater quality of life, positive mental health and social safeness—the perception that social environments are warm, reassuring and supportive. The largest simple correlation was with quality of life, at r = 0.553. Connectedness was also negatively correlated with anxiety and depressive symptoms, as expected. However, when the researchers entered all five outcomes into a multiple regression model, only quality of life, positive mental health and social safeness remained significant independent predictors of school connectedness. The model explained approximately 34.8 percent of the variance in connectedness, and quality of life showed the strongest unique association, with a standardized beta of 0.339.

That distinction matters because correlations do not establish direction or causation. A student who feels connected to school may experience greater well-being, but a student who already feels safe and satisfied with life may also be more likely to view school positively. The study’s cross-sectional design cannot determine whether school connectedness protects against poor mental health, whether mental health shapes perceptions of school, or whether both are influenced by other factors. The authors note that anxiety and depression were not significant independent predictors in the regression despite their negative correlations with connectedness. One possibility is that emotional symptoms and perceptions of school relationships operate through different pathways. Another is that the overlap among well-being measures altered the unique contribution of symptom scores when they were considered together.

The study has several additional limitations. All information came from adolescent self-reports, which can be influenced by memory, social desirability or a tendency to answer related questions in similar ways. The sample was drawn from public schools and included mainly students in grades seven through nine, so the results may not generalize to private schools, younger children, older adolescents or different educational systems. School-level characteristics—including size, culture, leadership and local norms—were not controlled for, even though they could affect students’ experiences. A ceiling effect was also observed for most of the connectedness items: more than 15 percent of participants selected the maximum response for several questions. Such clustering at the high end can make it harder for a scale to detect improvement among students who already report strong connectedness.

Despite those caveats, the revised measure could be useful in both research and practice because it reduces respondent burden while retaining strong reliability. A four-question tool can be incorporated into broader school surveys, repeated during intervention studies or used alongside mental-health screening without taking substantial classroom time. The shortened scale is focused specifically on students’ personal sense of belonging and connection to school. That focus is also its limitation. By removing the teacher-fairness question, the instrument no longer directly assesses whether students believe teachers treat them or other students fairly. The researchers recommend using an additional measure of student–teacher connectedness when that relationship is a central research or intervention target.

The findings point toward a broader shift in adolescent mental-health research: schools are increasingly being viewed not only as places where problems may be detected, but also as social environments capable of supporting well-being. Measuring whether students feel that they belong can help identify vulnerabilities that may be invisible in academic records or symptom checklists. The authors call for longitudinal studies involving multiple informants, including teachers and parents, as well as research in more diverse school settings and cultures. Future work should also test whether the four-item scale is sensitive to change after programs designed to improve school climate, peer relationships, mental well-being or quality of life. For now, the Portuguese validation provides evidence that a leaner measure can capture an important dimension of adolescent experience—while underscoring that connection to school and connection to teachers may not be exactly the same thing.