Abstract Background The aim of this study was to use Bronfenbrenner’s ecological theory to investigate adolescents’ school connectedness and family climate as potential predictors of depressiveness in adulthood. Methods The data are from the Northern Swedish Cohort and the sample consists of 481 women and 526 men born 1965 that participated in data collection at four time points, at age 16, 21, 30 and 43. Multivariate linear regression was used to examine the associations between school connectedness and family climate and depressiveness, respectively. Results Poor school connectedness was found to be associated with depressiveness up to mid adulthood and social/material adversities in adolescence were found to expand this association in young adulthood. Conclusions This study show that poor school connectedness can have long lasting effects on mental health. Thus, mental health promoting initiatives with holistic approach aiming at enhancing both sense of belonging in school, peer relations and academic achievements are needed. The study accentuates the complex processes determining mental health and propose a theoretical approach appealing for public mental health research. To advance the knowledge of the mechanisms behind the associations between proximal processes and depressiveness in adulthood, additional life-course studies are called for. Key messages Poor school connectedness can have long lasting effects on mental health. Initiatives aiming at enhancing both sense of belonging in school, peer relations and academic achievements are needed.