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A new analysis of data from a long-term national health study suggests that early adolescents who increase their social media usage over time may score lower on certain tests of brain function. The research indicates that even moderate engagement with these platforms is linked to slight declines in reading and memory skills as children transition into their teenage years. These findings appeared recently in a research letter published in the Journal of the American Medical Association.
Digital platforms have become a central part of modern childhood, yet the long-term impact on developing minds remains a subject of intense debate. Previous research regarding screen time has often lumped interactive social media with passive activities like watching television or playing video games. This lack of distinction has made it difficult for experts to isolate the specific effects of apps designed to capture and hold user attention through personalized feeds.
The investigation was led by Jason M. Nagata and colleagues at the University of California, San Francisco. The team sought to understand if patterns of usage over several years correlated with how well children performed on standardized cognitive assessments. They hypothesized that higher engagement with social platforms would correspond with lower scores in various intellectual domains.
A primary theory guiding this inquiry is known as the displacement hypothesis. This concept suggests that time spent scrolling through feeds replaces activities that build cognitive skills, such as reading books, sleeping, or completing homework. The researchers aimed to test this by observing changes in intellectual performance as children aged from roughly ten to twelve years old.
The team utilized data from the Adolescent Brain Cognitive Development study, which is a massive long-term project tracking brain development in the United States. They focused on a sample of 6,554 children who were between the ages of 9 and 10 when the data collection began. The researchers tracked these participants over a two-year period ending when they were approximately 12 or 13 years old.
Based on self-reported habits, the analysts categorized the children into three distinct groups to model their usage trajectories. The largest group, comprising nearly 58 percent of the participants, maintained no or very low social media use throughout the study period. A second group, representing about 37 percent, started with low use that gradually increased to an average of 1.3 hours per day.
The smallest group consisted of roughly 6 percent of the children. This cohort exhibited a sharp rise in activity, reaching more than three hours of daily social media use by the end of the period. The researchers then compared the cognitive scores of the two active groups against the group with little to no exposure.
To measure mental function, the study employed a standardized testing suite known as the NIH Toolbox. This battery of assessments evaluates various domains including reading recognition, vocabulary, and memory. The analysis adjusted for factors such as household income, parental education, and existing mental health symptoms to ensure fair comparisons between the groups.
The data revealed a consistent pattern where increased social media use tracked with lower cognitive scores on specific tasks. Adolescents in the “high increasing” group showed the most significant deficits compared to their peers who avoided social media. Specifically, these heavy users scored lower on tests measuring their ability to recognize words and recall sequences of pictures.
Performance on picture vocabulary tests also lagged in the high-usage group. This particular metric assesses stored language knowledge, often referred to as crystallized intelligence. The researchers noted that these specific deficits support the idea that screen time might be crowding out educational opportunities.
The study indicated that even the “low increasing” group experienced similar, though less severe, associations. Children who averaged just over an hour of daily use by age 13 still performed worse on reading and memory tasks than non-users. This implies that the threshold for potential negative effects might be lower than previously assumed.
Not all cognitive domains showed a negative association. The researchers did not find statistically significant deficits in the Flanker test, which measures attention and inhibitory control, or in pattern comparison processing speed. The negative impacts appeared concentrated in areas related to accumulated knowledge and memory rather than rapid processing.
While the correlations were statistically significant, the absolute difference in scores was relatively small. The average scores for all groups remained within the normal range for their age. This has led to differing interpretations regarding the practical importance of the findings.
In an accompanying editorial, Sheri Madigan and colleagues argued that these small shifts can matter significantly when applied to a whole population. They noted that “subtle differences in cognition at a group level may translate into students taking longer on average to complete assignments.” They suggested that these minor individual deficits could aggregate into broader educational setbacks.
The editorial authors distinguished between crystallized cognition and fluid cognition. Crystallized cognition involves skills acquired through learning and experience, such as vocabulary. Fluid cognition involves solving novel problems. The study found the largest differences in crystallized areas, which strengthens the argument that social media may displace time spent learning.
Beyond displacement, the editorial pointed to other potential mechanisms. They highlighted that social media features such as infinite feeds and notifications can disrupt sleep. Sleep is essential for brain maturation and memory consolidation during adolescence.
A major limitation of the study is its observational nature. It cannot prove that social media causes lower test scores, only that the two are related. It is possible that children with academic struggles are more prone to seeking out social media as a distraction.
Additionally, the data relied on children reporting their own screen time. Self-reporting is often inaccurate, as users tend to underestimate how much time they spend online. Future research will need to utilize more objective tracking methods to verify these usage patterns.
Reaction from the wider scientific community has been mixed. Chris Ferguson, a professor of psychology at Stetson University, expressed skepticism regarding the study’s conclusions. He stated, “The effect sizes reported are so small as to likely be the result of statistical noise.”
Ferguson argued that the study does not provide strong evidence for a causal link. He noted that youth cognitive performance is generally stable and that the observed fluctuations might not be meaningful. This perspective highlights the difficulty in separating genuine signals from random variations in large datasets.
Conversely, Victoria Goodyear from the University of Birmingham found the results consistent with broader trends in academic research. She remarked, “An interesting finding is that not only high, but lower levels of use are associated with worse outcomes.” This supports the notion that regulatory attention might be needed even for moderate usage.
The editorial argues that waiting for perfect data may prevent necessary protective measures. Madigan and her co-authors reference the Evidence to Decision framework. This framework assists policymakers in weighing imperfect evidence against the risks of inaction.
They contend that the potential for harm justifies a precautionary approach to social media policy. They write that “children, families, and societies cannot afford to wait for perfect evidence that will never come.” The authors suggest that enforceable age limits and improved design standards could mitigate these developmental costs.
The study provides a new data point in the ongoing effort to understand the “digital diet” of American youth. While it does not settle the debate on causation, it highlights a distinct pattern where increased screen time correlates with reduced performance in reading and memory. As digital platforms continue to evolve, understanding these trajectories will be essential for parents and educators alike.
The study, “Social Media Use Trajectories and Cognitive Performance in Adolescents,” was authored by Jason M. Nagata, Jennifer H. Wong, Kristen E. Kim, Racquel A. Richardson, Sahana Nayak, Char Potes, Andreas M. Rauschecker, Aaron Scheffler, Leo P. Sugrue, Fiona C. Baker, and Alexander Testa.
