Policy oriented tobacco research indicates that a number of interventions aimed at reducing access to tobacco among youth leads to significant declines in experimentation and tobacco use (58). Such interventions include laws placing age restrictions on the purchase of tobacco products and tax-driven increases in the price (and, by implication, availability) of tobacco products. Parallel research has indicated that self-reported measures of availability and age at first opportunity to use cannabis (59;60) are strong predictors of onset of cannabis use and tobacco smokers tend to report earlier opportunities to use cannabis (61). Intriguingly, there is evidence for genetic influences on self-reported availability (62). However, whether the effects of tobacco smoking on availability of cannabis are purely environmental or include activation of genetic vulnerabilities remains unexplored.
