Out-of-pocket costs are not the bottom line in financial toxicity.

Adolescent mental health has become a growing public health concern, with approximately one in five children and young people aged 8–25 in the UK identified as having a probable mental disorder in 2023 []. This growing crisis has prompted increased research into its underlying causes, with one area of particular focus being the role of children’s time allocation across different types of activities []. In recent years, as digital devices increasingly shape how adolescents communicate, access information, and spend their leisure time, concerns have emerged about their potential negative effects on psychological wellbeing []. Excessive digital time may displace essential activities such as sleep, physical exercise, and in-person social interactions, all of which are crucial for mental health []. It may also expose young people to online harassment, violent content, and unrealistic social comparisons, which can contribute to anxiety, depression, and reduced life satisfaction [, ]. The potential impact of digital engagement on adolescent wellbeing has been the subject of ongoing and highly scrutinized debates in academia, media, and political sphere, with policymakers in several countries, including the UK, considering measures such as banning smartphones in schools and restricting social media access for those under 16 []. Leading health institutions (e.g. the UK Royal College of Paediatrics and Child Health) have issued guidelines on recommended screen time levels to mitigate potential risks associated with excessive digital engagement []. Despite widespread concerns, existing research provides mixed evidence on the association between digital time and adolescent psychological wellbeing [, ]. While some studies report a significant negative relationship [, ], others find little to no clear evidence of harm [, ]. The association varies depending on the type of digital activity, population subgroups, amount of time spent, and whether engagement is active or passive. Additionally, findings differ by research data sources and methods used to examine these relationships. Most studies rely on self-reported time-use data, as well as cross-sectional and correlational designs, which are susceptible to recall bias and reverse causality []. In addition, previous research has largely focused on the amount of time spent on a specific digital activity of interest, framing the debate around whether increased or decreased digital time alone directly influences adolescent wellbeing. However, focusing on digital time in isolation neglects the broader context of time use within a fixed 24-h time constraint, failing to account for the interdependence and trade-offs between competing daily activities. The fixed constraint is a key concept in economic theories of resource allocation, which suggest individuals distribute their budget of time (and money) to maximize personal utility []. While financial constraints are less relevant for adolescents, time remains a limited resource: every hour spent on one activity is an hour not spent on another. Additionally, digital activities can compete with or complement other forms of daily engagement. For instance, an adolescent who spends hours gaming may engage less in physical activity, whereas another who connects with active peers on social media may be encouraged to spend more time outdoors. To better understand the impact of digital engagement, more comprehensive approaches are needed to examine how digital engagement fits into the broader context of daily time use.