The validity of the alcohol dependence PGRS was analysed by testing for association between polygenic risk for alcohol dependence and alcohol consumption. We then tested the association with cognitive ability test scores. Alcohol consumption was included as a fixed‐effect covariate for all analyses except where alcohol consumption was the dependent variable. Any association between polygenic risk for alcohol dependence and cognitive ability would therefore reflect genetic overlap between the traits without the confounding effect of alcohol consumption. Two models were fit to test these associations: an unadjusted model which had age, sex, alcohol consumption, four MDS components and the PGRS as fixed effects. An adjusted model was also fitted which included social deprivation and education as additional fixed effects.
