This is the first study of its kind to estimate the SNP heritability of generalized vulnerability to substance dependence and compare the genetic liability across multiple phenotypic definitions. The results provide an indication of the additive effect of common SNPs on nicotine, cannabis, cocaine, and alcohol in particular. Given the high loadings of these substances on the DD and PU factors, the additive effect of the common SNPs on individual substance dependence/problems ranges from ∼25-36%. Although DD evidenced the highest heritability, the effects attributed to common SNPs are highly correlated across the three phenotypes. Overall, the evidence supports the utility of common SNPs to index the genetic liability to substance addiction.
