"The present paper examined the extent and ordering of licit and illicit drug use across 17 disparate countries worldwide. This comparison, using surveys conducted with representative samples of the general population in these countries, and assessment involving comparable instruments, allowed for the first assessment of the extent to which initiation of drug use follows a consistent pattern across countries. Previous studies, concentrated in high income countries with relatively high levels of cannabis use, have documented: a common temporal ordering of drug initiation; an increased risk of initiating use of a drug later in the sequence once having initiated an earlier one; and the persistence of the association following controlling for possibly confounding factors (Kandel et al., 2006).

"The present study supported the existence of other factors influencing the ordering and progression of drug use because 1) other illicit drug use was more prevalent than cannabis use in some countries, e.g. Japan; 2) the association between initiation of 'gateway' drugs (i.e. alcohol/tobacco and cannabis), and subsequent other illicit drug use differed across countries, in some instances according to background prevalence of use of these gateway drugs; and 3) cross-country differences in drug use prevalence corresponded to differences in the prevalence of gateway violations.

"Higher levels of other illicit drug use compared to cannabis use were documented in Japan, where exposure to cannabis and tobacco/alcohol was less common. In this case, a lack of exposure and/or access to substances earlier in the normative sequence did not correspond to reductions in overall levels of other illicit drug use. This finding is contrary to the assumption that initiation reflects a universally ordered sequence in which rates of drug use later in the sequence must necessarily be lower than those earlier in the sequence (Kandel, 2002). This has not previously been reported as research has been traditionally conducted in countries where use of tobacco, alcohol and cannabis is relatively common."