The overall aim of this study was to investigate the association between family structure in childhood and mental health problems in young adulthood. A prospective cohort study was conducted with 481,777 individuals with complete follow-up information, which was obtained from national registers in Sweden. Individuals who were living with only one biological parent at age 17 were compared with those who grew up with two parents with regard to retrieval of prescribed psychotropic drugs at age 35. The association was examined by Cox regression analyses with equal survival time for all individuals included in the analyses. The results demonstrated a higher risk for retrieval of psychotropic medicines among the individuals who grew up with only one parent, with hazard ratio of 1,21 (95%CI: 1,19-1,23). The multivariate analyses showed that a part of the association was explained by familial and individual factors, namely parents’ country of origin, area of residence, parents’ and the individual’s educational attainment, receipt of social benefits and parents’ history of psychiatric disorder. The results indicated that the increased risk of mental health problems among individuals who grew up with only one parent might be accounted for by various psychological, social and economic factors associated to parental separation.