In conclusion, while analyses revealed some promising relationships of SNPs previously implicated in tobacco smoking with cannabis measures, these associations did not appear to be independent of their effects on smoking. As large meta-analyses of tobacco smoking have shown, by increasing sample sizes, common variants associated with cannabis involvement can also be successfully identified. Such discoveries will enhance our ability to identify such cross-disorder SNPs with greater precision, as has been witnessed for phenotypes such as schizophrenia, bipolar disorder, major depressive disorder and autism (Lee et al., 2013).
