Ordinary least squares regression was used to test the association of cannabis dependence symptoms with the interaction between rs604300 genotype and CA. Sex, age quartiles, one ancestrally informative principal component, and study of origin (FSCD or COGA) were included as covariates. As in CATS, additional covariates were entered representing the interactions between rs604300 and each covariate of no interest as well as CA and each covariate of no interest (Keller, 2014).
