Role of Genetic Risk in the Association Between Screen Time and Child Development—Reply

Abstract

COMMENT & RESPONSEIn Reply We appreciate the thoughtful comments on our study. 1 We agree with Takahashi et al that the association between screen time and child development may be determined more accurately if genetic information is considered. Developmental delays may include neurodevelopmental disorders (autism spectrum disorder or attention-deficit/hyperactivity disorder) and other genetic characteristics. Recent studies have shown that diverse psychiatric disorders and behavioral traits, including neurodevelopmental disorders, share common genetic factors. [2][3][4][5] Adjustments for genetic factors will be particularly important in identifying high-risk children who are vulnerable to screen time and in clarifying why screen time is associated with specific developmental domains.However, we disagree that it is difficult to narrow the bidirectional association between screen time and child development to a unidirectional association without adjusting for genetic risk. In the random-intercept cross-lagged panel model, lagged associations pertain exclusively to withinperson fluctuations, and stable traitlike between-person differences are separated as random intercepts. 6 That is, the model partially adjusts for genetic factors by separating developmental traits due to the individual's own genetic factors and tendencies of screen time due to the parenting environment, affected by the parents and the individual's own genetic factors as latent variables. However, one limitation of this analysis is that it cannot separately identify the effects of genetic and environmental factors on an individual or family, nor can it determine the extent to which children are genetically vulnerable to screen time.In addition, our analysis did not focus on developmental delays. It is important to note that a directional association was demonstrated between increased screen time and lower developmental scores in children, excluding those diagnosed with autism spectrum disorder. However, there may be a genetically at-risk population among children identified as having undiagnosed neurodevelopmental or psychiatric disorders before age 3 years. In some cases, environmental factors may protect against genetic risks. In such cases, the direction of the association between screen time and development cannot be properly assessed without considering the genetic factors. An analysis that considers the genetic risk of developmental delay would provide important information for both public health and medicine.Of note, our article 1 was corrected to fix an error in the Meaning section of the key points. The text inadvertently read, "In this study, increased screen time in early childhood was negatively associated with poor performance on developmental screeners." This association was not negative.