How Does the Time Children Spend Using Digital Technology Impact Their Mental Well-Being, Social Relationships and Physical Activity? An Evidence-Focused Literature Review

"Understandably, parents, teachers and others who have an interest in children's health and well-being become increasingly concerned as children spend more time using digital technology, but are also confused by the lack of consensus on whether this is good or bad for children."

Children's engagement with digital technology is increasing in all parts of the world, as are concerns about whether this is healthy or harmful. The main part of this paper from the United Nations Children's Fund (UNICEF) Office of Research - Innocenti reviews the body of evidence on the impact of time spent using digital technology on children's well-being across three dimensions: mental/psychological, social, and physical. The paper highlights that methodological limitations need to be more carefully considered in research, attributing the general lack of conclusive evidence to such limitations. The second part critically appraises what we know about the idea of addiction to technology and the popular science notion that digital technology might "re-wire" children's brains. Finally, recommendations for strengthening research practices in this area are offered.

The evidence-focused literature review includes studies of children aged 0-18 and encompasses literature published between 2005 and 2017, the period when digital technology became available for everyday use by children in Western societies and regular use became the norm. A broad definition of digital technology is used in this paper. It includes digital devices such as computers, tablets, and mobile phones, as well as the many digitally mediated activities that children engage in via these devices, such as using the internet, going on social networking sites, chatting online, or playing video games.

In summary, the evidence reviewed suggests that moderate use of digital technology tends to be beneficial for children's mental well-being, while no use or too much use can have a small negative impact. One study found that these positive and negative impacts were very small and not as relevant as other factors known to be of importance to children's mental well-being. This is in line with findings from a meta-analysis of 40 studies of both adults and children, where a negligible negative effect of internet use on well-being was reported. Instead of focusing only on the impacts of time spent on digital technology, it is suggested that researchers pay more attention to the influences of the content children encounter and the activities they participate in online, in addition to their social and family environments.

The evidence also suggests mostly positive outcomes from using digital technology in terms of children's social relationships. It is generally found that children's social relationships are stimulated by digital technology; while early research found indications of some negative impacts, these seem to have largely been attenuated, since the majority of a child's social circle is now online. However, research in this area sometimes struggles to measure children's time use appropriately, since it is difficult to determine when someone is socialising online and for how long, given that many children have near constant access. More research is needed on the potential negative effects of passively browsing social networking sites, as this might make children envious of other people's carefully crafted online personas, potentially leading to feelings of inadequacy.

The evidence reviewed here is mixed with regard to the impact on children's physical activity and does not provide much clarity. "The finding that screen-based activity and physical activity seem to be independent behaviours is particularly important for health promotion policies and should be underlined."

In the second part of the paper, the hypothetical idea of addiction to technology is introduced and scrutinised. This is followed by an overview of the hypothetical idea that digital technology might "hijack children's brains", an assumption that is challenged by recent neuroscience evidence. In sum, "the neurobiological mechanisms that may contribute to excessive use of digital technology are, so far, largely unknown. However, it is unlikely that digital technology can cause addiction by directly impacting the brain. Furthermore, claims that the brain might be hijacked or re-wired by digital technology are not supported by neuroscience evidence and should be treated with skepticism.... Unfortunately, both mass media and researchers sometimes misuse, misunderstand or exaggerate neuroscience findings, which leads to unhelpful narratives about hijacked brains, causing fear and confusion among the public."

In conclusion, the literature review found little support for the "displacement hypothesis", which posits that the harm posed by technology is proportional to exposure. While time spent on digital technology does, to some extent, take time away from other activities, which in some situations (such as periods of high volume of school work) can be problematic, current evidence does not suggest that this will have any major or long-lasting impact on children in the well-being dimensions reviewed here. Although many studies have been conducted, most suffer from theoretical, conceptual or methodological limitations, which make the results unreliable in terms of providing solid evidence of impact.

Recommendations are made to improve quality and reliability of research and debate in this area:

• Fine-tune measurement of children's digital engagement. Aggregate measures of "screen time" are conceptually problematic, as the different devices children use and the content of children's digital engagement are ignored.
• Carry out more longitudinal studies for hypothesis-testing confirmatory research. Most research up to now draws on cross-sectional data, which are helpful for hypothesis generation but unsuitable for hypothesis testing and for capturing long-term outcomes. The cumulative effects of spending a lot of time using digital technology from a young age are particularly important to study in future research.
• Consider children's life contexts and socio-demographics to the greatest extent possible. More control variables need to be included in quantitative studies to ensure that variables that have known effects on child well-being outcomes are not excluded. Children's online experiences cannot be studied in isolation from their lives in general.
• Strengthen reproducibility of research and the reliability of findings. There could be much to gain by encouraging researchers to register their hypotheses before collecting data and sharing the pre-registration protocol, data, and analysis code with each publication, following an "open science" approach. Such an approach can ensure that every policy-relevant research finding is produced in a transparent way and is computationally reproducible and that all materials are freely accessible online, where they can be vetted by colleagues.
• Support more nuanced media reporting, given the conflicting evidence base. All too often news articles share evidence from single studies, or studies that are methodologically weak or that exaggerate or misrepresent the results. To aid journalists, science communication by researchers and universities needs to be improved to reflect accurately research findings, their generalisability, and limitations.