In this prospective cohort study, we explored associations of childhood socioeconomic status (SES) with social connection in adulthood, and to which extent these associations can be explained by SES in adulthood. We used data from the longitudinal Young Finns Study (n=1,775, 3-18 years at baseline). Childhood SES was assessed through parental income and educational attainment in 1980, and participants' own adult SES through income and educational attainment in 2007. The outcomes were three indicators of social connection measured in 2018-2020: 1) loneliness, 2) perceived social support and 3) frequency of social contact. SES indicators were analyzed separately using regression models and causal mediation analysis via marginal structural models. In the mediation analyses, low parental income was associated with higher loneliness, lower perceived social support, and less frequent social contact in adulthood while adjusting for parental and own educational attainment. The associations with loneliness and perceived social support were partially mediated by participants' income in adulthood. Conversely, the associations between parental educational attainment and social connection in adulthood were smaller, with confidence intervals including the null. These results emphasize that poor family financial conditions during childhood may have long-lasting implications for the development and maintenance of social connection throughout the lifespan.

Keywords: childhood environment; loneliness; prospective study; social contact; social support; socioeconomic status.