Competing accounts of the gateway effect: the field thins, but still no clear winner.

© 2006 The Authors. Journal compilation © 2006 Society for the Study of Addiction Addiction, 101 , 470–476 Deciding which of these causal pathways explains the relationships between cannabis and other illicit drug use will depend upon a convergence of evidence from a variety of sources, such as: animal studies of the plausibility of pharmacological mechanisms (e.g. [7]); studies of twins discordant for cannabis use (e.g. [8]); studies of the impact of the Netherlands cannabis policy on the ‘gateway pattern’; and evaluations of drug education interventions to see whether delaying cannabis use reduces rates of other illicit drug use [2]. Whatever future research reveals about the causal explanations of the relationship between cannabis and other illicit drug use, it is no longer possible to regard the relationship as an artefact of residual confounding with little or no policy significance.