Measures

Emotional well-being and self-esteem were measured using the self-report KINDL for children and adolescents, which is a well validated tool for measuring health-related quality of life in children and adolescents [13]. KINDL consists of six domains, physical, emotional, self-esteem, family, friends, and school. We focused on the emotional and self-esteem domains in the present study. Each domain is assessed using four questions, in which the participant chooses an answer from five categories (never, seldom, sometimes, often, or always) on quality of life in the past week. Each question is scored from 1 (never) to 5 (always), and a total is calculated for each domain. We transformed the scores into percentage scores, with a score of 100 representing the best quality of life in that domain (corresponding to a score of 5 for all four questions).

As a measure of the stringency of social distancing policies, we utilized the COVID-19 Stringency Index by the Oxford COVID-19 government response tracker, which measures the stringency of containment and closure policy indicators for various countries [14]. The Index is computed using nine metrics of social distancing policy: school closures, workplace closures, cancellation of public events, restrictions on public gatherings, closures of public transport, stay-at-home requirements, public information campaigns, restrictions on internal movements, and international travel controls. The Index is calculated for each country on any given day, by taking the mean score of the nine metrics, taking a value between 0 and 100. Gender (male or female) and age group at baseline (6–11 or 12–17 years old) were used as covariates.