Participants and Procedures

Participants were part of the Korean Children & Youth Panel Survey 2010 (KCYPS 2010) by the National Youth Policy Institute (NYPI) in South Korea¹. This is a large-scale longitudinal survey on the development of Korean children and adolescents. KCYPS annually traced three different panel cohorts for 7 years from 2010 to 2016 that were selected based on a stratified multi-stage clustering sampling method. Data were collected using self-report questionnaires for adolescents and their parents.

For the purposes of this study, we used data from two panels. Panel 1 (2003 birth cohort) included 2,342 participants (boys = 1,211, girls = 1,131) who were 6–7 years old (First grade in elementary school in Korea) at the baseline (T1). Panel 2 (2000 birth cohort) included 2,378 participants (boys = 1,245, girls = 1,133) who were 9–10 years old (Fourth grade in elementary school) at the baseline (T1). For Panel 1, of the initial sample of 2,342 participants, 90.4, 88.3, and 85.5% participated in the study at T4, T6, and T7, respectively. For Panel 2, of the initial sample of 2,378 participants, 93.3, 84.8, 86.7, and 83.2% participated at T3, T5, T6, and T7, respectively. Selective attrition analysis revealed that, in both panels, no significant differences existed between families who stayed versus dropped out of the study over time in terms of child sex, parent education, family income, inattention, depressive symptoms, and peer relationships measured at the baseline.