This week a new meta-analysis titled "How Early Digital Experience Shapes Young Brains During 0-12 Years: A Scoping Review," by Wu and colleagues was published in Early Education and Development.

This work is less a meta-analysis than a summary of studies that explore the brain (both structurally and functionally) and how it relates to screen time differences. The authors report associations with various parts of the brain and advise educators and parents to pay attention. In the Discussion, they conclude: “...digital experience could cause structural and functional changes in children’s frontal, parietal, temporal, and occipital lobes, brain connectivity, and brain networks. And the most vulnerable area is the prefrontal cortex and its associated executive function.”

However, a closer look reveals that about 90% of the studies are cross-sectional. This means screen time and brain measures are taken simultaneously and merely correlated with each other. The issue here is that one cannot infer causality. Screen usage might be causing changes in the brain, or a common factor could influence both brain development and the propensity to use screens (see discussion about this in Klingberg et al. 2021). 

One such underlying factor is the home environment. Screen usage is closely linked to socioeconomic status (SES), parental income, and education. Research from our group (Judd et al. 2020, PNAS) and others has demonstrated how SES impacts brain development.

Genetics is another potential underlying factor. It's well-known that children in homes with more books tend to have better language skills. However, parents provide more than just an environment; they also pass on their genes. A set of genes positively linked to parents' reading ability leads to more books in the home. The same genes affect the children's reading ability, but the number of books might do nothing to the children's reading ability.

A more effective research design is the longitudinal approach, which examines how an environmental factor correlates with subsequent changes in behavior or brain structure. Findings from such studies can sometimes be the opposite of what one might conclude from a cross-sectional study. An example is our study of over 4000 children and video gaming (Sauce et al. 2022).

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At the first time-point (i.e., corresponding to a cross-sectional analysis), we found a small negative association between IQ and time spent playing video games. However, after tracking the change in IQ over two years, we observed that video gaming was positively associated with IQ development. This suggests that the initial negative correlation was due to self-selection, with less academically inclined children preferring video games. Interestingly, there were also correlations between genetic predisposition, SES, and the amount of time children spent gaming.

Regarding Wu et al.'s meta-analysis, only four of the studies were longitudinal. Three of these not only came from the same research group but also focused on the same group of about 200 Japanese children. The meta-analysis overlooked a more recent study by Wilson, which involved over 4000 children and found no link between digital media usage and brain connectivity.

Studying the impact of digital media on a child's brain development is challenging. However, this doesn't mean we should make hasty conclusions from insufficient studies; it underscores the need for more comprehensive and improved scientific research.

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References:

Dandan Wu, Xinyi Dongb, Danqing Liub, and Hui Li (2023)  How Early Digital Experience Shapes Young Brains During 0-12 Years: A Scoping Review. Early Education and Development, DOI: 10.1080/10409289.2023.2278117

Bruno Sauce, Magnus Liebherr, Nicholas Judd, Torkel Klingberg (2022) The impact of digital media on children’s intelligence while controlling for genetic differences in cognition and socioeconomic background. Scientific reports, 12 (1), pp. 7720, 2022.

Torkel Klingberg, Nicholas Judd, Bruno Sauce (2021) Assessing the impact of environmental factors on the adolescent brain: the importance of regional analyses and genetic controls. World psychiatry, vol. 21,1 (2022): 146-147. doi:10.1002/wps.20934

Judd et al. (2020) Cognitive and brain development is independently influenced by socioeconomic status and polygenic scores for educational attainment. Proceedings of the National Academy of Sciences, 117 (22), pp. 12411–12418, 2020, ISSN: 0027-8424.