Reuters

From the perspective of drug warriors, the criminal laws against drug possession are all that protect Americans from a deluge of drugs, an orgy of marijuana, cocaine, heroin and methamphetamine use that would kill children, destroy productivity and basically leave America a smoking hulk of wasteland populated by brain-dead zombies.

For example, one opponent of marijuana decriminalization wrote in a 2009 forum in the New York Times that the policy would lead to “hundreds of billions of dollars in new medical-care costs, traffic and other accident costs, reduced worker productivity and lower educational achievements.” (More on Time.com: Is Drug Use Really on the Rise?)

But new research on Portugal’s drug policy suggests that this isn’t necessarily so. Portugal decriminalized possession of all drugs in 2001. The outcome, after nearly a decade, according to a study published in the November issue of the British Journal of Criminology: less teen drug use, fewer HIV infections, fewer AIDS cases and more drugs seized by law enforcement. Adult drug use rates did slightly increase — but this increase was not greater than that seen in nearby countries that did not change their drug policies. The use of drugs by injection declined.

Of course, there’s no way of knowing which, if any, of these changes were caused by the change in policy — without a control group, this kind of research cannot determine cause and and effect. But Portugal started with one of the lowest rates of drug use in Europe — far lower than American rates — and remains below the EU average. For example, 19% of 15-to-16-year-olds in Europe in general have tried marijuana at least once, compared with 13% of Portuguese people that age. The figure for U.S. high school sophomores is 32%. (Related Links: Why Drinking Like a Guy is Worse for Women)

“The most important direct effect was a reduction in the use of criminal justice resources targeted at vulnerable drug users,” says Alex Stevens, professor of criminal justice at the U.K.’s University of Kent, who co-authored the study. “Before, a large number of people were being arrested and punished for drug use alone. They saved themselves a lot of money and stopped inflicting so much harm on people through the criminal justice system. There were other trends since drugs were decriminalized in 2001, but they are less easy to attribute directly to decriminalization.”

Under Portugal’s decriminalization policy, users are not arrested but referred by the police to a “dissuasion” commission. The commission is made up of three people, typically an attorney, a social worker and a medical professional. It determines whether the person is addicted — if so, they can be referred to treatment or given specific penalties like being banned from a particular neighborhood or losing a driver’s license. Treatment is not forced, however, and those who are not addicted are often not sanctioned in any way. Only about 5% to 6% of users are brought before such commissions a second time in the same year. (More on Time.com: Addiction Files: Recovering From Drug Addiction, Without Abstinence)

Stevens says the positive changes in HIV/AIDS rates and a decline in opioid-related deaths are probably more linked with an expansion of treatment than with decriminalization alone. The number of users in treatment increased by 41% — going from 23,654 to 38,532 between 1998 and 2008. “Releasing funds from [enforcement] allows you to spend more on treatment,” says Stevens.

The changes in teen drug use were complex: throughout Europe, teen drug use rose sharply during the period in which Portugal decriminalized and then fell — the same trend was seen in Portugal but the fall was steeper.

Mark Kleiman, director of the drug policy analysis program at UCLA and author of When Brute Force Fails: How to Have Less Crime and Less Punishment, is skeptical that Portugal’s policy holds any lessons for the U.S. other than that the “U.S. and UN look silly for getting hysterical,” about Portugal’s move. “The bottom line [is that] no clear disaster resulted from decriminalization.” (More on Time.com: Addiction Files: Recovering From Drug Addiction, Without Abstinence)

Stevens concurs. “The main claim we make is that decriminalization did not lead to the kinds of disaster that were anticipated by opponents,” he says.

In the debate over California’s marijuana legalization initiative, little attention was paid to the fact that Governor Schwarzenegger signed a bill decriminalizing the possession of up to an ounce of marijuana — a relaxation of state drug law that would have been much more controversial had the state not faced the possibility that voters would support full legalization of sales as well as possession. Eleven other states have also decriminalized — though this does not always prevent the arrest of users for possession. (More on Time.com: Is Marijuana Addictive? It Depends How You Define Addiction)

With 1.5 million Americans being arrested each year for simple drug possession — 40% of them for marijuana — Portugal’s experience raises the question of whether arresting users is a cost-effective use of taxpayer money. Billions of dollars are spent each year on enforcement of drug possession laws and that enforcement is notoriously racially biased — if ceasing to arrest users for possession has essentially no effect, is this really a good way to spend scarce money?

More on TIME.com:

Decriminalizing Drugs in Portugal

7 Ways to Regulate Marijuana Effectively