Screen time linked to ADHD symptoms

Children who spend longer looking at screens have more severe attention-deficit/hyperactivity disorder (ADHD) symptoms, according to Japanese scientists who studied brain development and behavioural issues. The study found evidence that children with higher screen time exhibit measurable differences in the volume and thickness of several key brain areas.

This is not the first time that screen time in childhood has been linked with ADHD, but the new research adds fresh understanding of the neural mechanisms underlying development. Qiulu Shou, Masatoshi Yamashita, and Yoshifumi Mizuno at the University of Fukui, Japan, published findings of their large-scale study in Translational Psychiatry.

The researchers used data from the Adolescent Brain Cognitive Development study in the United States, tracking 11,878 children initially aged 9 to 10 years over a two-year period. Based on advanced magnetic resonance imaging data and parent-reported behaviour assessments, the team found clear evidence of a developmental link: longer daily screen time at baseline was a significant predictor of increased ADHD symptoms after two years, even after controlling for initial symptom severity levels.

‘This study is the first to examine the relationship between screen time, ADHD symptoms, and brain structure from a developmental perspective using such a large-scale database,’ explains Dr Shou.

Screen time was also associated with developmental abnormalities in multiple key brain structures. At baseline, it was linked to a smaller total volume of the cortex and reduced volume in a region known as the right putamen, which plays a key role in language learning, addiction, and reward-related processes. After two years, screen time was associated with hindered development of cortical thickness in regions vital for cognitive functions, including the right temporal pole and specific areas of the left frontal gyrus.

One of the findings of this study centered on the role of brain structure as a mediator of ADHD symptoms. Statistical analyses suggest that total cortical volume partially mediates the relationship between screen time and ADHD symptoms at baseline. This means that the observed association between longer screen time and greater ADHD symptom severity is, at least in part, explained by the observed smaller cortical volume. The team suggests that excessive screen exposure may contribute to a delayed brain maturation pattern that is often observed in children with ADHD.

‘Our work provided some evidence toward growing concern about the association between digital media exposure and children’s mental and cognitive health,’ said Dr Yamashita. ‘The results provide some neuroscientific evidence for the need to control screen time.’

Overall, this study paves the way for further investigation that may guide both the technology industry and the educational sector toward designing digital environments that support, rather than hinder, children’s cognitive growth.