The epidemiology of drug use disorders cross-nationally: Findings from the WHO's World Mental Health Surveys

Background: Illicit drug use and associated disease burden are estimated to have increased over the past few decades, but large gaps remain in our knowledge of the extent of use of these drugs, and especially the extent of problem or dependent use, hampering confident cross-national comparisons. The World Mental Health (WMH) Surveys Initiative involves a standardised method for assessing mental and substance use disorders via structured diagnostic interviews in representative community samples of adults. We conducted cross-national comparisons of the prevalence and correlates of drug use disorders (DUDs) in countries of varied economic, social and cultural nature. Methods and findings: DSM-IV DUDs were assessed in 27 WMH surveys in 25 countries. Across surveys, the prevalence of lifetime DUD was 3.5%, 0.7% in the past year. Lifetime DUD prevalence increased with country income: 0.9% in low/lower-middle income countries, 2.5% in upper-middle income countries, 4.8% in high-income countries. Significant differences in 12-month prevalence of DUDs were found across country in income groups in the entire cohort, but not when limited to users. DUDs were more common among men than women and younger than older respondents. Among those with a DUD and at least one other mental disorder, onset of the DUD was usually preceded by the ‘other’ mental disorder. Conclusions: Substantial cross-national differences in DUD prevalence were found, reflecting myriad social, environmental, legal and other influences. Nonetheless, patterns of course and correlates of DUDs were strikingly consistent. These findings provide foundational data on country-level comparisons of DUDs.