May 3, 2004

Dutch drug policies do not increase marijuana use, first rigorous comparative study finds

By Jennifer McNulty

In the first rigorous study comparing marijuana use in the Netherlands and the United States, researchers have found no evidence that decriminalization of marijuana leads to increased drug use. The results suggest that drug policies may have less impact on marijuana use than is currently thought.

The findings appear in the May issue of the American Journal of Public Health. Craig Reinarman, professor of sociology at UCSC, coauthored the article, “The Limited Relevance of Drug Policy: Cannabis in Amsterdam and in San Francisco,” with Peter D. A. Cohen, director of the Centre for Drug Research (CEDRO) at the University of Amsterdam in the Netherlands, and Hendrien L. Kaal, now an instructor at the University of Leiden in the Netherlands.

The study compared the cannabis (marijuana and hashish) habits of users in Amsterdam and San Francisco to test the premise that punishment for cannabis use deters use and thereby benefits public health.

“We compared representative samples of experienced marijuana users to see whether the lawful availability of marijuana did, in fact, lead to the problems critics of the Dutch system have claimed,” said Reinarman. “We found no evidence that it does. In fact, we found consistently strong similarities in patterns of marijuana use, despite vastly different national drug policies.”

Highlights of the study include:

• The mean age at onset of use was 16.95 years in Amsterdam and 16.43 years in San Francisco.

• The mean age at which respondents began using marijuana more than once per month was 19.11 years in Amsterdam and 18.81 years in San Francisco.

• In both cities, users began their periods of maximum use about two years after they began regular use: 21.46 years in Amsterdam and 21.98 years in San Francisco.

• About 75 percent in both cities had used cannabis less than once per week or not at all in the year before the interview.

• Majorities of experienced users in both cities never used marijuana daily or in large amounts even during their periods of peak use, and use declined after those peak periods.

The Netherlands effectively decriminalized marijuana use in 1976, and it is available for purchase in small quantities by adults in licensed coffee shops; in the United States, marijuana use carries stiff criminal penalties, and more than 720,000 people were arrested for marijuana offenses in 2001.

The study was funded by the U.S. National Institute on Drug Abuse (NIDA) and the Dutch Ministry of Health.

In identical questionnaires administered in Amsterdam and San Francisco (cities chosen for their similarities as politically liberal northern port cities with universities and populations of roughly 700,000 people), nearly 500 respondents who had used marijuana at least 25 times were asked detailed questions about their marijuana use. The questionnaire explored such issues as age at first use, regular and maximum use, frequency and quantity of use over time, intensity and duration of intoxication, career use patterns, and use of other illicit drugs.

“In the United States, marijuana policy is based on the assertion that strict penalties are the best way to inhibit use,” said Reinarman.

The study’s findings cast doubt on that scenario, he said. Despite widespread lawful availability of cannabis in Amsterdam, there were no differences between the two cities in age at onset of use, age at first regular use, or age at the start of maximum use.

The study found no evidence that lawfully regulated cannabis provides a “gateway” to other illicit drug use. In fact, marijuana users in San Francisco were far more likely to have used other illicit drugs--cocaine, crack, amphetamines, ecstasy, and opiates--than users in Amsterdam, said Reinarman.

“The results of this study shift the burden of proof now to those who would arrest hundreds of thousands of Americans each year on the grounds that it deters use,” said Reinarman.

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