cannabis use has notable effects on use of harder drugs (42; 43). However, these studies also note that these prevention strategies are not drug-specific and hence, generally reduce exposure to risk influences that correlate with early use of cannabis and later experimentation with harder drugs. While prevention studies rely on social mechanisms of causation (i.e. early cannabis use causes use of hard drugs via exposure to deviance-prone environments), a rodent study has noted that adolescent exposure to cannabis, even when controlling for environmental similarity, leads to increased preference for other drugs (e.g. opiates)(44), implicating biological mechanisms, such as cross-sensitization. Although widely cited in support of the gateway hypothesis, such preclinical studies focus on the process of drug sensitization, which occurs after onset of use, rather than initiation of use and therefore are not applicable to the gateway hypothesis.
