Screens and The Adolescent Brain: Excessive Screen Time in Pre-Adolescence Predicts ADHD and Slower Brain Growth

This research discusses how increased screen time among adolescents is related to sleep, behavior, and mental health, especially ADHD symptoms. Studies show that prolonged screen use may be associated with changes in the brain and an increase in symptoms of impulsivity and inattention, although not always intensely. A longitudinal study with thousands of children observed that increased screen time was linked to a gradual increase in ADHD symptoms and small changes in cortical structure. The relationship exists, but is still considered moderate and requires further research to understand whether it is a cause or a consequence.

In recent years, the time adolescents spend in front of screens, such as cell phones, tablets, computers, and televisions, has increased in several countries. This growth became even more evident during and after the COVID-19 pandemic. Screen time directly influences important daily life habits, such as the amount of physical activity and the quality and duration of sleep.

Furthermore, research indicates that this behavior can negatively affect the mental health, brain development, and social behavior of young people.

Adolescence is a particularly sensitive period, as it is during this phase that profound changes occur in the body, brain, and identity. Therefore, many experts recommend limiting screen time, even though in practice many teenagers still spend long hours exposed to digital devices.

When we analyze the relationship between screen time and mental health, several studies show that the greater the daily time spent in front of screens, the greater the likelihood of developing behaviors associated with Attention Deficit Hyperactivity Disorder (ADHD).

This disorder is characterized by difficulties with attention, impulsivity, and, in some cases, physical hyperactivity. Research indicates that long periods in front of screens are associated with an increase in the severity of these symptoms and even a higher risk of meeting the diagnostic criteria for ADHD.

However, it is important to note that other studies show that this relationship, although it exists, is usually weak. In other words, increased screen time does not necessarily mean that the adolescent will have ADHD, and in many cases the observed impact is not considered clinically relevant.

In addition to behavioral issues, researchers have also investigated how screen use relates to structural changes in the brain. Some research indicates that screen time may be associated with subtle changes in the development of white and gray matter in regions such as the prefrontal cortex, the orbitofrontal cortex, and the anterior cingulate cortex, areas related to emotional control, decision-making, and action planning.

However, other larger studies have not found consistent evidence of these changes. This suggests that effects may exist, but are likely small or vary depending on the type of use, age, family environment, and other influences.

Mechanisms have also been proposed to explain how screen time can influence ADHD-related symptoms. Among these mechanisms, two stand out: impulsivity and sleep quality. The theory is that the constant consumption of fast-paced digital content with immediate rewards can stimulate impulsive behaviors.

Furthermore, excessive screen use, especially at night, can impair sleep, and poor sleep is linked to increased symptoms of inattention and hyperactivity.

Another line of research suggests that the relationship between screens and ADHD symptoms may involve neurological changes, such as delayed cortical development or reduced gray matter volume, found both in individuals with ADHD and in young people exposed to long periods of screen time.

Despite the growing scientific interest, most studies conducted so far have been cross-sectional, meaning they analyzed participants at only one point in time. This type of study helps to find associations, but it doesn't allow us to say whether screen time causes changes in the brain or in ADHD symptoms, or whether children predisposed to ADHD simply seek more screen time.

To better answer these questions, researchers used data from the ABCD study, one of the largest longitudinal studies on child development in the world, involving more than 11,000 children followed over time.

In this study, researchers analyzed data from over ten thousand children between nine and ten years of age and followed some of them two years later. They assessed how much time the participants spent in front of screens, the presence and evolution of ADHD symptoms, and characteristics of brain structure obtained through neuroimaging.

The analysis indicated that children who spent more time on screens showed a slight, but statistically significant, increase in ADHD symptoms over time. Furthermore, greater screen time was associated with a reduction in cortical thickness in specific brain regions. It was also observed that total cortical volume played a mediating role, albeit modest, in the relationship between screen time and ADHD symptoms.

This figure visually and simply shows how the time children spend using screens (such as cell phones, computers, tablets, or TVs) is related to changes in brain structure. The colored brain areas in the maps (A, B, and C) indicate where this relationship was observed. The stronger the blue color, the greater the negative relationship, meaning that more screen time is linked to a smaller volume or thickness in these regions. In panel A, we see the brain areas related to the volume of the cortex (the outer part of the brain). In panel B, the image highlights the right putamen, an internal brain structure important for functions such as motivation and motor control, showing that it also appears to decrease with more screen time. In panel C, the colors represent changes in cortical thickness, which is important because the thickness of this layer is linked to cognitive development. Graphs D and E show points representing thousands of children: the further to the right on the graph (more screen time), the lower the volume of the putamen and the total cortical volume tend to be. The blue lines indicate the general trend of this relationship; even though the points are scattered, the slope of the line shows that there is a pattern: more screen time is linked to a slightly smaller brain volume. In short, the figure indicates that more time in front of screens is associated with small reductions in parts of the brain involved in cognitive, motor, and emotional functions, suggesting that excessive use may affect brain development over time.

These results suggest that there is a relationship between screen time, brain changes, and ADHD-related symptoms, although the observed effects are not large and still need to be explored more deeply.

The study contributes to the understanding of the mechanisms that connect the digital environment to neurodevelopment and reinforces the need for more research, especially experimental and longitudinal studies, to determine whether these changes are causal or the result of more complex interactions between biological predisposition and lifestyle.

READ MORE:

Association of screen time with attention-deficit/hyperactivity disorder symptoms and their development: the mediating role of brain structure

Shou Q, Yamashita M, And Mizuno Y. 

Transl Psychiatry 15, 447 (2025) 

https://doi.org/10.1038/s41398-025-03672-1

Abstract:

The association among screen time, attention-deficit/hyperactivity disorder (ADHD) symptom development, and brain structure, and the neural mechanisms underlying the association between screen time and ADHD symptoms remain unclear. This study examines the relationships between the three using large-scale longitudinal data from the Adolescent Brain Cognitive Development (ABCD) study. Data on screen time, ADHD symptoms (measured via the Child Behavior Checklist), and brain structure were extracted from 10,116 children at baseline (ages 9–10) and 7880 children at a two-year follow-up. A linear mixed-effects model was used to assess the association between baseline screen time and changes in ADHD symptoms and brain structure after two years. Additionally, the mediating role of brain structure on the association between screen time and ADHD symptoms was examined. The results showed that screen time was associated with increased ADHD symptoms (β = 0.032, p = 0.001) and reduced cortical thickness in specific regions (right temporal pole: β = −0.036, false discovery rate (FDR)-corrected p = 0.020; left superior frontal gyrus: β = −0.028, FDR-corrected p = 0.020; and left rostral middle frontal gyrus: β = −0.030, FDR-corrected p = 0.020). Total cortical volume partially mediated the relationship between screen time and ADHD symptoms (β = 0.001, p = 0.023) at baseline. These findings suggest that screen time is associated with ADHD symptoms and brain structure, as well as their development, potentially providing insights into the neural mechanisms underlying the association between screen time and ADHD symptomatology.