Early screen time not a cause of autism, study concludes

A new study published in JAMA Pediatrics investigated whether screen time in early childhood increases the risk of autism spectrum disorder (ASD) later in life. While initial analyses suggested a positive association between early screen time and ASD, the researchers found this link disappeared after accounting for socioeconomic factors.

ASD is a developmental condition that affects how a person communicates, interacts socially, and processes information. It is called a “spectrum” because it encompasses a wide range of abilities and challenges, varying greatly from person to person. Some individuals with autism may have difficulty with speech and understanding social cues, while others may excel in specific skills like memory or pattern recognition. Autism is typically diagnosed in early childhood, and while its exact causes are not fully understood, a combination of genetic and environmental factors is believed to contribute.

The researchers conducted the study to explore whether behaviors like early screen time exposure could influence the development of ASD. Early childhood is a critical period for cognitive and social development, making it important to understand how environmental factors might shape these processes. Screen time, as a modifiable behavior, has become a growing concern due to its dramatic increase in recent decades.

“A substantial proportion of my research is focused on the interplay of genetic and environmental factors in autism. This study focuses on understanding potential links between early screen time and the risk of ASD because screen time exposure during early childhood is a modifiable behavior. Exploring its impact on ASD risk could provide critical insights for early intervention strategies and policy development,” said study author Ping-I (Daniel) Lin, an adjunct associate professor at the University of New South Wales and an associate professor at Saint Louis University School of Medicine.

The study used data from the Longitudinal Study of Australian Children, a large cohort dataset that tracks the development of children over time. The sample included 5,107 children, with a weighted population size of 243,046, to ensure the findings could be generalized. Screen time exposure was measured at two years of age based on weekly hours spent watching television, videos, or internet-based programs. At 12 years of age, parent-reported ASD diagnoses were recorded.

The researchers employed advanced statistical methods to analyze the data. Initially, they used multivariable logistic regression to examine whether early screen time was associated with ASD diagnosis while controlling for factors such as sex, family income, and maternal education. They then applied an instrumental variable method to isolate the potential influence of screen time from other confounding variables. This method allowed them to determine whether the association between screen time and ASD was causal or merely correlated due to shared socioeconomic factors.

The results initially showed a significant association between greater screen time at two years of age and an increased risk of ASD at 12 years. Specifically, children who had more than 14 hours of weekly screen time were nearly 1.8 times more likely to receive an ASD diagnosis compared to children with less screen exposure.

However, when the instrumental variable method was applied, the association disappeared. The analysis revealed that socioeconomic factors, particularly family income and maternal education, influenced both screen time exposure and ASD risk, suggesting that these factors, rather than screen time itself, accounted for the observed relationship.

“It was surprising that the association between early screen time and ASD risk disappeared when socioeconomic factors like family income and maternal education were accounted for as instrumental variables,” Lin told PsyPost. “These instrumental variables can be used to reduce selection bias when we evaluate the association between screen time and ASD risk, so the association results are more robust. This highlights the complexity of ASD risk factors and the potential role of broader social determinants.”

The study’s authors emphasized that while their findings suggest no causal relationship between early screen time and ASD, the results have important implications for clinical practice and policy. Clinicians could consider asking about screen time as part of a broader developmental assessment, as this behavior might indicate families in need of additional resources or support. Addressing underlying socioeconomic factors could help mitigate developmental risks more effectively than focusing solely on limiting screen time.

“The main takeaway is that while early screen time is associated with ASD in initial analyses, this association was not found to be causal when controlling for socioeconomic factors,” Lin explained. “Instead, screen time may serve as a marker for identifying families who could benefit from additional support, rather than being a direct risk factor for ASD.”

Despite its robust methods, the study has limitations. The reliance on parent-reported ASD diagnoses introduces the potential for misclassification, although prior research has shown strong stability in these reports over time. Additionally, the instrumental variable approach, while powerful, depends on the assumption that the chosen socioeconomic factors influence ASD risk only through their effect on screen time. Unmeasured variables or residual confounding may still play a role, and the study cannot rule out all alternative explanations.

“The long-term goals are to better understand modifiable early-life exposures that contribute to ASD risk and to identify social and environmental factors that could mitigate developmental risks, thereby informing targeted interventions and support strategies,” Lin said. “Specifically, optimizing ASD support may need to factor in socioeconomic factors such as racial disparities and health inequalities will be one of my long-term goals for this line of research.”

“Clinicians should consider asking about screen time during early childhood as part of broader developmental assessments. This behavior may signify the need of additional resources to address underlying socioeconomic challenges that could influence child development.”

The study, “Screen Time Before 2 Years of Age and Risk of Autism at 12 Years of Age,” was authored by Ping-I. Lin, Weng Tong Wu, and Yue-Liang Leon Guo.