U.S. has highest levels of illegal cocaine and cannabis use

A survey of 17 countries has found that despite its punitive drug policies the United States has the highest levels of illegal cocaine and cannabis use.

The study, by Louisa Degenhardt (University of New South Wales, Sydney, Australia) and colleagues, is based on the World Health Organization's Composite International Diagnostic Interview (CIDI) and is published in this week's PLoS Medicine.

The authors found that 16.2% of people in the United States had used cocaine in their lifetime, a level much higher than any other country surveyed (the second highest level of cocaine use was in New Zealand, where 4.3% of people reported having used cocaine). Cannabis use was highest in the US (42.4%), followed by New Zealand (41.9%).

In the Americas, Europe, Japan, and New Zealand, alcohol had been used by the vast majority of survey participants, compared to smaller proportions in the Middle East, Africa, and China.

The survey found differences in both legal and illegal drug use among different socioeconomic groups. For example, males were more likely than females to have used all drug types; younger adults were more likely than older adults to have used all drugs examined; and higher income was related to drug use of all kinds. Marital status was found to be related to tobacco, cannabis, and cocaine use, but not alcohol use (the never married and previously married having higher odds of lifetime cocaine and cannabis use than the currently married; tobacco use is more likely in people who have been previously married while less likely among the never married).

Drug use "does not appear to be simply related to drug policy," say the authors, "since countries with more stringent policies towards illegal drug use did not have lower levels of such drug use than countries with more liberal policies." In the Netherlands, for example, which has more liberal policies than the US, 1.9% of people reported cocaine use and 19.8% reported cannabis use.

Data on drug use were available from 54,068 survey participants in 17 countries. The 17 countries were determined by the availability of research collaborators and on funding for the survey. Trained lay interviewers carried out face-to-face interviews (except in France where the interviews were done over the telephone) using a standardized, structured diagnostic interview for psychiatric conditions and drug use. Participants were asked if they had ever used alcohol, tobacco, cannabis, or cocaine.

The study's main limitations are that only 17 countries were surveyed, within these countries there were different rates of participation, and it is unclear whether people accurately report their drug use when interviewed. Nevertheless, the findings present comprehensive data on the patterns of drug use from national samples representing all regions of the world.

Citation: Degenhardt L, Chiu W-T, Sampson N, Kessler RC, Anthony JC, et al. (2008) Toward a global view of alcohol, tobacco, cannabis, and cocaine use: Findings from the WHO World Mental Health Surveys. PLoS Med 5(7): e141. doi:10.1371/journal.pmed.0050141.