Decriminalizing marijuana doesn't lead to more widespread use, according to a new study comparing the drug's users in Amsterdam and San Francisco. The study, published in the May issue of the American Journal of Public Health, flies in the face of prohibitionists who argue that relaxed laws will lead to a rampant increase in the use of marijuana. Drug warriors, who often talk about marijuana being a first step to the use of harder drugs, should also take note that decriminalization appears to reduce the so-called "gateway effect."

The study compares Amsterdam and San Francisco, two politically left-leaning port cities with universities and populations of about 700,000. The authors compared the cannabis habits of users in the two cities to test the premise that punishment for cannabis use deters use and thereby benefits public health.

Co-author Craig Reinarman, professor of sociology at the University of California, Santa Cruz, says his work shows critics of Dutch decriminalization are dead wrong about the problems they predicted.

"In fact, we found consistently strong similarities in patterns of marijuana use," Reinarman says, "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 2 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.

Co-author Craig Reinarman is with the Department of Sociology, University of California, Santa Cruz, Calif. Co-authors Peter Cohen and Hendrien Kaal are with the Centre for Drug Research (CEDRO), University of Amsterdam, the Netherlands.

Marsha Rosenbaum, director of the Safety First project of the Drug Policy Alliance, and Ira Glasser, president of the Alliance board of directors, were among those who reviewed and commented on the study prior to its publication.

The researchers collected data from 500 people who used marijuana 25 times or more in their lifetimes. Data collection for the study was conducted between 1994 and 1999. The study was funded by the National Institute on Drug Abuse (NIDA) and the Dutch Ministry of Health.