To the editor

The pervasive presence of digital devices in children's lives has raised significant apprehensions about the impact of screen time on early childhood development [1]. Concerns about physical, cognitive, and socioemotional risks dominate the discourse despite advancements in technology presenting unique opportunities for learning and engagement for children [2]. The systematic review by Lee et al. [3] provides valuable insights that contribute to this deliberation. However, certain conceptual and methodological limitations in their analysis warrant closer scrutiny. This commentary examines these gaps, explores ongoing debates and implications for research and policy.

There is ongoing debate on the potential of well-designed digital media to affect infants’ cognitive development [4]. Data from a large sample of parents, indicated that when considering factors like child ethnicity, age, gender, and family socioeconomic status, the recommended screen time limits by the American Academy of Pediatrics may not be universally applicable [5]. Although some studies suggest that interactive educational apps can foster early literacy and problem-solving skills, most commercial apps lack scientific validation and are designed primarily for entertainment rather than learning. Poorly designed apps could often distract children more than educate them, offering limited developmental benefits. Rigorous evaluation of digital media content and adherence to evidence-based learning principles are essential for realizing the positive effects of screen time. This could have significant implications for screen time guidelines, which must be updated to account for the differing cognitive demands and engagement levels of various screen activities [2,4].

The discussion by Lee et al. [3] regarding the rise of portable smart devices among preschoolers in their review is timely, given the increasing shift from stationary media, such as television, to personal devices like smartphones and tablets. While increased portability has led to greater screen exposure and duration, the critical issue remains the uncertain impact of this increased usage on cognitive development and behavioral outcomes. Interestingly, longitudinal studies in older children have indicated both positive and negative impacts of passive screen time on structural and functional changes in different lobes of the developing brain, and neuronal connectivity [6].

Differentiating active and passive screen use is crucial for understanding its impact on child development, as the quality of screen time significantly outweighs the quantity [4]. Passive screen time, such as television viewing, is reportedly associated with sedentary behavior and adverse health outcomes such as obesity, low bone mineral density, elevated levels of cardiovascular risk factors, and more aggressive and antisocial behaviors [7]. Cognitively active screen time, including interactive games and educational apps, can promote cognitive engagement and may influence physical behaviors [1,8]. The current review unfortunately, does not distinguish between active and passive modes of screen engagement [8]. This lack of clarity makes it difficult to make any effort to draw meaningful comparisons across studies and hampers the formulation of nuanced guidelines.

Further, the studies by Sweetser et al. [8] and Madigan et al. [9] which fulfill the eligibility criteria have been overlooked in the systematic review. Sweetser et al. [8] highlighted the importance of distinguishing between active and passive screen time in understanding developmental outcomes. In a large-scale longitudinal study among Australian children, they contended that equating all screen-related activities is problematic. The cohort study by Madigan et al. [9] on the other hand, provided strong evidence for understanding directional associations between screen exposure and developmental outcomes. This longitudinal analysis, which assessed over 2,000 mother-child dyads, highlighted the cumulative nature of screen time’s impact, suggesting that early exposure can influence cognitive and socioemotional development. The analysis by Lee et al. [3] would have benefited from incorporating such studies, which fulfilled their research criteria, in formulating a nuanced approach that addresses both the quantity and quality of screen exposure.

The current review includes a diverse range of studies but lacks a standardized “definition of screen time,” which varies significantly depending on whether the activity involves passive consumption (e.g., television viewing) or active interaction (e.g., video games, educational apps). This lack of consistency obscures the interpretation of findings and limits the ability to draw robust conclusions about specific screen use types and their respective impacts. As Lee et al. [3] have already stated, extensive reliance on parental self-reports for screen time assessment has a significant impact on the validity of the research. Parental reports, though practical for large-scale data collection, are prone to considerable recall and social desirability biases. These biases can lead to either underestimation or overestimation of actual screen time, compromising data accuracy [10]. More objective methods, such as digital usage logs or wearable tracking devices, would enhance reliability by providing direct measures of screen exposure. For instance, a combination of interviews, mail back questionnaires, time-use diaries, and interviewer observations were used in the study by Sweetser et al. [8].

Cultural factors influencing screen time habits need further emphasis. Fully accounting for cultural variability across and within regions is complex. However, it is valuable to highlight cultural factors shaping children's media use. For instance, while the authors include studies from diverse regions, including Europe, North America, and East Asia, they do not explore how cultural differences in parenting norms, media availability, and socioeconomic contexts shape children's media use. This is particularly relevant given that cultural norms can significantly influence the extent to which screens are integrated into daily routines. For example, low daily exposure to smartphones in South Korea, where cultural norms around early academic preparation and technology use may drive prevailing trends. Moreover, parental modeling of appropriate screen behavior, such as limiting their own screen use and prioritizing non-screen activities, has been consistently shown to influence children's media habits [10]. Therefore, culturally specific influences need to be addressed in future research to ensure that policy recommendations remain relevant and applicable across diverse populations.

It is notable that more than three-fourth of the research included in this review are cross-sectional studies. Limited number of longitudinal studies is unfavorable to the power of the research findings to infer causality regarding the long-term effects of early screen exposure and to formulate evidence-based guidelines. The authors aptly call for longitudinal research designs for disentangling these complex relationships and understanding how screen time patterns evolve over critical early developmental stages. However, a more in-depth analysis of cultural factors, environmental contexts, and the differential impacts of various screen activities is warranted. Future research addressing these gaps is essential for developing comprehensive and culturally sensitive guidelines that balance the potential educational benefits of digital media with its developmental risks. As illustrated in Fig. 1, multiple determinants and subdeterminants shape the impact of screen time on childhood development. Interdisciplinary collaboration between researchers, educators, policymakers, and industry stakeholders will be vital in shaping evidence-based approaches to regulating screen time in early childhood.

Current evidence links excessive screen use to adverse health outcomes, including obesity, sleep disturbances, and emotional dysregulation [1,2,8]. A calibrated approach that accounts for the duration, content, and context of exposure is essential for assessing its neurobiological and socioemotional impacts. Emerging research indicates that overexposure to digital media may alter neural pathways involved in attention and emotional regulation, potentially contributing to attention deficits and behavioral issues. Practical guidelines should emphasize not only limiting overall screen time but also regulating when and how screens are used to minimize disruptions to sleep and family interactions.