To some extent, sequence of drug use reflects ease of access and youth may use cigarettes and tobacco prior to cannabis due to its availability. However, there is now growing support for reverse gateways (the use of cannabis prior to and increasing the risk for tobacco use) (19-21). Patton and colleagues (22) found that, while a majority of teenagers smoked cigarettes prior to experimenting with cannabis, in a subset, first use of cannabis preceded onset of cigarette smoking, representing a reversal of the conventional sequence (23;24). Whether these individuals represent a unique group or whether growing evidence for reverse gateways reflects increasing ease of access to cannabis relative to cigarettes, sale of which to minors may now be more stringently monitored, remains to be investigated.
