The psychosocial environment and especially various psychosocial risks in childhood have been shown to predict later negative health behavior and health problems. In this study, we examined whether various psychosocial factor domains in childhood and adolescence: socioeconomic status, theemotional family environment (parental nurturance, life-satisfaction), parental lifestyle, life-events, the child's self-regulatory behavior and the child's social adaptation were associated with body mass index (BMI) trajectories individually by domain and as a cumulative score across domains. The participants were a nationally representative sample of 2016 men and women fromthe Young Finns study aged 3-18 years at study entry in 1980. Their BMI wasmeasured at six study phases from 1980 to 2012. Their parents reported all the factors related to their psychosocial environment in 1980. The participants responded to questions on adulthood socioeconomic status in 2007. The accumulation of psychosocial factors in childhood was the main exposure variable. The findings fromrepeated measuresmultilevelmodeling showed that parental lifestyle and life-events and the more positive cumulative psychosocial factors score were associated with a slower increase in BMI during follow-up (regression coefficient range from - 0.06 to -0.50). In conclusion, the psychosocial environment in childhood and adolescence, particularly parental lifestyle and lack of stressful life-events, are associated with a lower increase of BMI. (C) 2017 Elsevier Inc. All rights reserved.