et al., 2011). Alternatively, genes related to cigarette use may also be linked to onset of cannabis use, such as brain-derived neurotrophic factor (BDNF). The BDNF variant rs6265 has been linked to cigarette use at p = 1.8 × 10−8 (Tobacco and Genetics Consortium 2010). A recent study also related this variant to cannabis use (Agrawal et al., 2015). Another study examining polygenic scores derived from a genomewide association study of tobacco smoking found these scores to predict a modest but significant proportion of variance in cannabis use as well (Vink et al., 2014).
