In future cross-national surveys, bioassays of drug use might be included. In the interim, we must use population survey data such as these to complement macro-level taxation records that summarise only legal alcohol and tobacco use across countries. These data are reasonable for developed countries, but are likely to significantly underestimate consumption in some developing countries. The findings of this study are consistent, however, with data collected in some countries from other epidemiological studies, which have been consistent with the findings here. The large cross-national differences documented here are consistent with approximations of drug use levels given in the United Nations World Drug Report [43] and with country-specific research—for example, researchers have documented high levels of cannabis use and early onset alcohol use in New Zealand [44], early onset alcohol use in Europe, and cocaine use in the US [45].
