Cannabis as a gateway drug: an examination and evaluation of potential causal mechanisms.

An ongoing debate within the literature concerns whether cannabis is a ‘stepping-stone’ or ‘gateway’ drug which leads to future hard drug use. There is particular disagreement over the causal mechanisms involved, and whether the relationship between cannabis and hard drug use is a direct effect due to cannabis use per se, or an indirect effect due to underlying predispositions and social factors relating to cannabis use. This paper examines and evaluates such explanations of the potential causal mechanisms involved and the variables which mediate this relationship. It is concluded that psycho-physiological and neurological, social, genetic and environmental explanation can all in part account for the statistical relationships observed between cannabis and hard drug use. However, it may be that cannabis has its gateway effects through a number of potential mechanisms, with no one mechanism accounting fully for observed relationships. A further consideration is given to what specifically constitutes a direct gateway effect.