Children today are growing up in a world increasingly dominated by digital media (DM) – from smartphones and tablets to video games and social networks. The average American child now spends nearly 5 hours per day engaging with these technologies, on top of any schoolwork or homework-related screen use. This rapid rise in DM usage has understandably sparked concerns about its potential effects on the developing brains of young people.

A team of researchers led by Samson Nivins at the Karolinska Institutet in Sweden sought to shed light on this pressing issue. In a landmark longitudinal study published in the journal Scientific Reports, they examined how different types of DM usage – including social media, video games, and television/video viewing – impact the structural development of key brain regions in children over a 4-year period.

“The general term ‘digital media’ encompasses a wide range of activities, each of which could influence brain development in distinct ways,” explains Nivins. “So it was important for us to look at these elements individually, rather than just lumping them all together.”

The researchers drew their data from the Adolescent Brain Cognitive Development (ABCD) study, a large-scale, long-term project following over 11,000 children in the United States from ages 9-10 through adolescence. At yearly intervals, the children reported their estimated daily usage of various DM activities. Every two years, they also underwent magnetic resonance imaging (MRI) scans to track changes in their brain structure over time.

Nivins and his colleagues focused their analysis on three key brain regions: the cerebral cortex, the striatum, and the cerebellum. The cortex, which makes up the outer layer of the brain, is known to play a crucial role in higher cognitive functions like intelligence. The striatum is involved in motor control, learning, and reward processing. And the cerebellum, traditionally associated with movement coordination, has more recently been implicated in a range of cognitive and emotional processes.

Surprisingly, the researchers found that overall DM usage did not significantly alter the developmental trajectories of the cortex or striatum. “We initially hypothesized that certain types of digital media, like video games, might be associated with increases in cortical surface area, which has been linked to intelligence,” Nivins says. “But that wasn’t the case.”

However, the team did observe some intriguing patterns when it came to the cerebellum. Children who spent more time using social media showed a subtle decrease in cerebellar volume over the 4-year period, with the developmental trend accelerating later in adolescence. In contrast, those who devoted more time to playing video games exhibited a small but statistically significant increase in cerebellar volume during this critical window of brain maturation.

“The cerebellum is a brain region that’s particularly sensitive to environmental influences, both during the prenatal period and throughout childhood and adolescence,” explains Nivins. “So it makes sense that we’d see some impacts there, even if the overall effect sizes were quite small.”

These findings raise interesting questions about the potential mechanisms underlying the observed associations. One possibility is that the constant distractions and frequent task-switching inherent in social media use could disrupt the natural pruning and myelination processes happening in the cerebellum during this developmental stage. Conversely, the more focused, goal-oriented nature of video game play may provide cognitive stimulation that supports cerebellar growth.

“Of course, these are just hypotheses at this point,” cautions Nivins. “We really need more research, especially longitudinal studies with even longer follow-up periods, to fully understand the long-term implications of these trends.”

Another key consideration is the clinical relevance of the effect sizes observed in this study. While the researchers did find statistically significant associations between DM usage and cerebellar development, the actual magnitude of these effects was quite small – an annual change of just 0.05, which the team deemed “meaningful” given the potential for accumulation over time.

“In the field of psychology and neuroscience, there’s an ongoing debate about what constitutes a truly meaningful effect size,” explains Nivins. “The traditional benchmarks proposed by Cohen are often criticized as being arbitrary, and there’s increasing recognition that effect sizes need to be considered in context.”

For example, even a small effect on something like attention could have significant real-world consequences if it impacts a child’s academic performance or social functioning over the course of their development. Conversely, an effect that seems quite large in the moment may ultimately be mitigated by habituation or compensatory mechanisms.

“With DM usage, we’re talking about a behavior that’s becoming increasingly ubiquitous in modern childhood,” Nivins notes. “So even small impacts on the brain could potentially accumulate to produce meaningful differences at the individual level.”

The researchers also found that socioeconomic status (SES) played an important role in brain development, with children from lower-SES backgrounds exhibiting smaller cortical surface areas and cerebellar volumes compared to their higher-SES peers. This aligns with a growing body of research demonstrating the profound influence of environmental factors, including family income and neighborhood quality, on the structural and functional maturation of the brain.

Interestingly, the team did not observe any significant interactions between SES, DM usage, and brain development. This suggests that the effects of digital media were consistent across socioeconomic lines, rather than being amplified or dampened by a child’s broader environmental context.

Similarly, the researchers did not find any sex differences in the relationships between DM usage and brain structure. “This was a bit surprising, given that we know boys and girls often engage with digital media in quite different ways,” says Nivins. “But it seems the underlying neural mechanisms may be similar, at least when it comes to the specific brain regions we examined.”

One limitation of the study is its reliance on self-reported DM usage data from the children themselves. While previous research has shown adolescents can provide reasonably reliable estimates of their own screen time, there’s always the potential for recall bias or inaccuracy. The researchers note that parent-reported screen time was consistently lower than child-reported, highlighting the challenges in obtaining precise behavioral measures.

Additionally, the survey questions used in the ABCD study didn’t capture certain nuances, such as the timing of DM use (e.g., daytime vs. nighttime) or the specific genres of video games played. These factors could potentially influence brain development in different ways.

“We also weren’t able to look at the potential interactive effects of using multiple forms of digital media simultaneously,” Nivins points out. “In the real world, kids often have smartphones, tablets, and gaming consoles all competing for their attention at the same time. Untangling those complex usage patterns is an important area for future research.”

Despite these limitations, the study’s longitudinal design and large, diverse sample size lend considerable weight to its findings. And the researchers hope their work will help spur further investigation into this rapidly evolving area of child and adolescent development.

“It’s clear that digital media is now an integral part of most young people’s lives, for better or for worse,” says Nivins. “As scientists, we have a responsibility to understand how these technologies are shaping the next generation’s brains and cognitive abilities. Only then can we provide parents, educators, and policymakers with the evidence-based guidance they need to ensure kids are getting the most out of the digital world while minimizing the risks.”

Ultimately, the story of digital media and brain development is a complex one, with no easy answers. But studies like this one are crucial steps toward unraveling that complexity – and charting a course forward that protects the wellbeing of today’s youth.