The study looked at cannabis use among 15-year-old adolescents in thirty European and North American countries in 2002, 2006, and 2010. The overall results showed a significant decline in cannabis use. Affluent countries in Western and Southern Europe and North America (Belgium, Canada, Denmark, France, Germany, Ireland, Italy, Netherlands, Portugal, Spain, the United Kingdom, USA) showed a decrease in frequent cannabis consumption among 15-year-old boys and/or girls.
But the emerging market countries that have recently experienced a rapid increase in their GDP showed stable or increasing cannabis use. In three of the twelve former communist countries in Eastern, Central, and Southern Europe, cannabis use increased among boys (FYR Macedonia, Latvia, Lithuania) and in one, it increased among girls (Russia). In the remaining nine countries, cannabis use among 15-year-olds appears to have stabilized over time. Adolescents from less affluent countries seem to have adopted consumption patterns consistent with their peers in richer countries.
The recent decrease in cannabis use in richer countries and among higher socioeconomic status groups could be explained by the recently increased attention on the harmful effects of substance use for young people and the subsequent implementation of public health prevention measures aimed at reducing substance use. Thus, while wealth in earlier decades fostered adolescent substance use due to increased opportunities for use, nowadays, national health policies in wealthy countries may have contributed to the observed decrease of adolescent cannabis use.