Mingyang Li1, Ruoke Zhao1, Xixi Dang2, Xinyi Xu1, Ruike Chen1, Yiwei Chen1, Yuqi Zhang1, Zhiyong Zhao1, and Dan Wu1
1Department of Biomedical Engineering, Zhejiang University, Hangzhou, China, 2Department of Psychology, Hangzhou Normal University, Hangzhou, China
Synopsis
Keywords: Adolescents, Adolescents, screen use, reading, brain volume, brain development
Motivation: The causal relationships between screen use and mental health were not clear.
Goal(s): We used genetic, imaging, and questionnaire data from ABCD study to investigate the causal relationships between screen use and mental health in early adolescents.
Approach: One-sample Mendelian randomization analysis.
Results: We found a direct causal relationship between screen use and behavior problems and an indirect effect between screen use and brain volume by the changes in reading habits.
Impact: These findings provide new
evidence for a causal influence of screen use and reading habits on brain
development and highlight the importance of monitoring media use and related
habits change in children.
Introduction
The rise of new media has greatly changed our
lifestyles, leading to increased time spent on new platforms and less time
spent reading 1,2. Previous studies have found associations between
screen use and mental health in children 3–8. However, the causal relationships between screen
use and specific outcomes need further elucidation. Causal analysis has become possible with advanced statistical
tools, such as the Mendelian randomization (MR) analysis 9, which uses genetic variation as a tool to infer
causal relationships between two variables. Therefore, we aim to investigate
the causal associations between screen use on neuroimaging, cognition, and behavior
in young adolescents, and the potential displacement (or competing) effect
between screen use and reading habits.Method
Participants: This study utilized data from the Adolescent Brain Cognitive Development
(ABCD) study (v4). We excluded preterm-born infants with gestational age less
than 37 weeks (n = 1629). And randomly excluded one participant from each pair of
twins/siblings with a close gene relationship (pi-hat > 0.4). Finally, 7107
subjects remained at baseline and 4505 at two-year follow-up.
Exposure, outcome, and confounding variables
The study focused on six different exposure
variables related to screen use 10,11 (e.g. TV shows or movies, videos, video games,
texting, social networks, and video chatting) and reading time 12.
The outcome variables in this study included five
cognitive abilities assessed by the NIH Toolbox 11,13 and eight behavioral problems in the CBCL 11,14 (Fig 2).
Neuroimaging traits included brain volumes of 160 regions
estimated using the Destrieux and ASEG atlas 15,16. T1-weighted images were included in an optimized
MRI acquisition protocol (FOV: 256 x 256, 1.0 x 1.0 x 1.0mm, TR = 2500ms, TE = 2.88ms, Flip angle = 8°) that is harmonized to be compatible across three 3T
scanner platforms: Siemens Prisma, General Electric 750, and Phillips at 21
sites. And were preprocessed following the ABCD preprocessing pipeline 17.
We adjusted for common confounding variables in our
study, including age, sex, household income, parental education, race,
ethnicity, prematurity, sibling, and site effect.
Statistical analyses: We first
used a linear mixed-effects model to explore the consistent association between
the exposures and outcomes at two waves(e.g. baseline and two-year follow-up). Then
we performed a one-sample MR analysis on the variables that had significant
associations. We further employed a mediation analysis and a two-step MR
analysis to examine whether screen use indirectly influences the outcomes by
changing reading habits (Fig 1 shows the flowchart). Bonferroni correction was
applied at each time point for non-neuroimage outcome variables, and FDR
correction was applied for neuroimage variables.Results
The linear mixed-effects
model revealed consistently significant adverse associations between screen use
and cognitive abilities, behavioral problems (corrected p < 0.05, Fig 1a), and brain volume in 32 regions (corrected p < 0.05, Fig 1b) at two time points.
In contrast, reading habits showed significant positive associations with all
cognitive abilities (Fig 1a) and brain volumes in 85 regions (Fig 1b), widely
distributed in the temporal and frontal regions.
MR analysis further
revealed significant causal effects among the above associations. For instance,
negative causal effect between TV use and oral reading recognition (β = -2.93, corrected p < 0.007, Fig 3a), and between
reading habits and brain volume in 22 regions including the prefrontal, and temporal
(corrected p < 0.05, Fig 4). Interestingly, increased screen use was
identified as a result, rather than a cause, of certain behavioral issues such
as rule-breaking and aggressive behaviors (Fig 3b).
Regarding the displacement effect, we found a
significant negative association between screen use and reading habits (β = -0.10 to -0.02, corrected p < 0.05, Fig 5a), and a significant
mediation effect of screen use on the reading-related outcomes (Fig 5b). The two-step MR analysis further showed that
screen use causally decreases reading time (Fig 5c), and indirectly impacts
language abilities (Fig 5d). Specially, although screen use did not directly
alter the brain volume, but it indirectly reduced brain volume via reducing
reading time (Fig 5e).Discussion and Conclusion
Our study employed MR
analysis to investigate the causal impact of screen use and reading on brain development
in early adolescents. The results indicate that screen use has both direct and
indirect effects on brain development. On the other hand, it is important to
avoid exaggerating the negative consequences of screen use, as some behavioral
problems may precede and contribute to excessive screen use. In summary, these
findings underscore the importance of monitoring media use and the associated
changes in habits resulting from media exposure. Acknowledgements
This work was supported by
the Ministry of Science and Technology of the People’s Republic of China (2021ZD0200202),
the National Natural Science Foundation of China (81971606, 82122032), and the
Science and Technology Department of Zhejiang Province (202006140, 2022C03057).
Data used in the
preparation of this article were obtained from the Adolescent Brain Cognitive
DevelopmentSM (ABCD) Study (https://abcdstudy.org), held in the NIMH
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