BackgroundThe COVID-19 pandemic has fundamentally changed social life within a very short time. Lockdown policies often consider the trade-off between containing the spread of the pandemic and the negative impact for the economy. Policy makers should pay more attention to the psychological and social impacts of the lockdown.ObjectivesHow did the mental health of adolescents in Germany change during the first wave of the COVID-19 pandemic and the lockdown in Germany?Material and MethodsAnalyses are based on longitudinal data from Germany and a random sample of the birth cohorts 2001-03. Respondents were 15-17 years old at the first interview in 2018/19. 854 adolescents participated in the second wave of the survey in May and June 2020. Depressiveness is assessed with the State-Trait Depression Scale.ResultsDuring the first lockdown, adolescents show a significant increase in depressive symptoms. Prior to the lockdown, 10.2 percent had clinically relevant depressive symptoms [CI: 8.0; 12.4]. In spring 2020, the prevalence increased to 25.2 percent [CI: 22.0; 28.4]. Young women have a significantly higher risk of developing depressive symptoms than men of the same age. Immigrant background is an equally strong risk factor. The prevalence of depressive symptoms among adolescents with an immigrant background increased from 11% to 33%.DiscussionTo address this increased mental health risk and the inequalities, policy makers and society should ensure access and availability of target-group-specific and low-threshold prevention and counselling.