ABSTRACT
This preregistered longitudinal study examined changes in adolescents' depressive and anxiety symptoms before and during the COVID-19 pandemic using latent additive piece-wise growth models. It also assessed whether support from and conflict with mothers, fathers, siblings, and best friends explained heterogeneity in change patterns. One hundred and ninety-two Dutch adolescents (Mean age: 14.3 years; 68.8% female) completed online biweekly questionnaires for a year (November 2019-October 2020), consisting of a prepandemic, lockdown, and reopening phase. Depressive symptoms increased following the lockdown and decreased upon reopening. Anxiety symptoms showed an immediate decrease followed by a gradual increase in the reopening phase. Prepandemic family and best friend support and conflict did not explain heterogeneity in depressive and anxiety symptoms during the COVID-19 pandemic.