We used data from the youngest cohort of the Finnish Twin Cohort Study (FinnTwin12) when twins were in young adulthood (aged 20–26 years). We fitted a series of linear mixed models to examine whether relationship status moderates the association between GPS and alcohol misuse. We then tested for sex differences in these interactions. All analyses adjusted for age, sex, educational attainment and current student status. Linear mixed models were adjusted for clustering at the family level. We checked for the robustness of our results by assessing separate models that included interactions between GPS, relationship status and each covariate [41].
