Screen time may affect brain development in early childhood

In preschool-aged children, higher digital media use (screen time) was associated with lower cortical thickness (CT) and sulcal depth (SD), according to a secondary analysis of data collated for an MRI-based study.

“[These brain areas] support primary visual processing and higher-order functions such as top-down attention, complex memory encoding, letter recognition, and social cognition,” said the researchers.

Despite the AAP* recommendation of limiting screen time in kids, its use is on the rise and has been amplified during the COVID-19 pandemic. [Pediatrics 2016;138:e20162591; www.commonsensemedia.org/sites/default/files/research/report/2020_zero_to_eight_census_final_web.pdf, accessed January 28, 2023] Given the increasing role of digital media today, “it is critical to understand the direct and indirect impacts of various aspects of use on emerging skills and underlying neurobiology,” they stressed.

The team sought to evaluate the correlation between digital media use and established measures of cortical morphology, particularly during early childhood when plasticity is high. Fifty-two children (n=29 girls; mean age 52.7 months) with acceptable MRI image quality participated. [Sci Rep 2022;12:19095]

In the whole-brain analyses, higher ScreenQ** scores were associated with lower CT in extensive clusters located in bilateral yet right-lateralized occipital, parietal, temporal, and fusiform regions (two-tailed p-FDR***<0.10) and lower SD in two clusters in the right fusiform cortex (two-tailed p-FDR<0.05).

For the ROI^#-based analyses, higher ScreenQ scores were tied to lower CT in the bilateral cuneus, left lingual gyrus and right precuneus, and superior parietal and supramarginal gyri (two-tailed p-FDR<0.05). Higher ScreenQ scores were also associated with greater SD in the right cuneus and lesser SD in the right fusiform gyrus (two-tailed p-FDR<0.05).

Results for both analyses were obtained after controlling for age and sex.

Implications

“The most extensive and significant clusters were in the right-lateralized occipital and superior parietal regions that support both sensory (eg, cuneus) and multimodal associative (eg, supramarginal gyrus) processes, suggesting impacts in areas expected to be mature at this age and in others that are expected to still be developing,” they said.

Lower CT in the lingual gyrus has been associated with lower episodic memory and social cognition in adults. [bioRxiv 2018;doi.org/10.1101/289447] Lower CT in the right supramarginal gyrus, which supports empathy, has been linked to conduct disorder in adolescents. [Soc Cognit Affect Neurosci 2015;10:302-310] Evidence has linked excessive and inappropriate digital media use to lower empathy, and a ‘video-deficit’ in social cognition in preschool-aged children. [Pediatrics 2017;140 (Suppl 2):S71-S75; Media Psychol 2017;22:23-38] Though speculative, the lower CTs in these areas may reflect underdevelopment at this age, the researchers noted.

Greater CT and SD in the fusiform cortex has been tied to higher reading abilities and emergent literacy skills. [Dev Cogn Neurosci 2020;45:100856; Pediatrics 2021;147:e20201641] “[W]hile also speculative, the current findings may be a biomarker of impacts of higher screen-based media use on cortical surface area supporting reading at this age,” they said.

Longitudinal studies needed

Participants were mostly from families of higher income and maternal education. As such, the results might change with greater socioeconomic diversity. Also, as the study was confined to children who completed MRI and met certain motion criteria, the findings might not be extrapolated to those with other behavioural characteristics.

“[Nonetheless,] while several findings are unclear and/or speculative [owing] to the complex nature of cortical development, this study provides novel evidence that differences in brain structure related to screen-based media use are evident during early childhood [and may become more extensive over time],” said the researchers.

They called for longitudinal studies to further characterize longer-term effects on cognitive-behavioural, social-emotional, and overall development.