WASHINGTON, Dec. 2 (UPI) -- Marijuana use among adolescents does not appear to act as a "gateway" leading to the use of harder drugs such as cocaine and heroin, researchers reported Monday.
A mathematical model developed by the think tank RAND Corporation of Arlington, Va., challenges the long-held belief that marijuana should be illegal because it leads to heroin and cocaine abuse. Policymakers often cite this as a rationale for keeping the drug illegal even for medicinal uses.
The model, which simulated adolescent drug use in the United States, found chance rather than marijuana use is a better explanation for why kids might go on to use harder drugs, Andrew Morral, associate director of RAND's Public Safety and Justice Unit and lead author of the study, told United Press International.
"All the evidence used to support the gateway effect can be accounted for by chance using a model that has no gateway effect," Morral said. His team used surveys on drug use from 1982 to 1994 to construct a model representative of adolescent drug usage in the United States. The model assumed some kids were more likely to use drugs due to genetics or their environment -- as supported by real world evidence. It did not assume there was a gateway effect. That is, kids who used marijuana were not assumed be more likely to use harder drugs.
The model produced results fairly close to current U.S. drug use patterns, Morral said. "In many ways, the model is simpler and more compelling than the gateway model" because it does not require the additional assumption of the gateway effect to explain how kids begin using cocaine and heroin, he said. Science favors the simplest explanation or the one that requires the least number of assumptions.
Morral noted there is some evidence to support the gateway effect. For example, marijuana users are much more likely than nonusers to use hard drugs, and the more marijuana a person smokes the more likely he or she is to use hard drugs. "But this evidence is not definitive," he said. "There are other plausible explanations for why these associations are found."
Young people often get their first opportunity to use marijuana years before they get their first opportunity to use harder drugs, Morral said. "Kids with a propensity to use drugs will use whatever drugs they have an opportunity to use," he said. "And so they use marijuana first" because it is readily available.
Morral pointed out his findings are in line with other scientific evidence casting doubt on the gateway hypothesis for marijuana. For a while, scientists have been questioning the gateway theory, he said, noting a 1999 report from the Institute of Medicine in Bethesda, Md., concluded the evidence did not support the notion of a gateway effect.
Marijuana advocates said Morral's study, which appears in the December edition of the journal Addiction, confirms their own observations.
"It doesn't surprise me," Paul Armentano, spokesperson for the National Organization for the Reform of Marijuana Laws in Washington, told UPI. "NORML has maintained for some time (the gateway effect) is really just smoke and mirrors," he said.
The U.S. Drug Enforcement Administration had not seen the study and was unable to comment on it. But DEA spokesman Will Glaspy told UPI the agency's position is "a high majority" of the cocaine and heroin users in the U.S. first used marijuana.
Morral said marijuana use comes first because it is the first drug available, not because it leads to harder drugs.
Armentano also refuted the DEA's position.
"It's clear that for the overwhelming majority of Americans marijuana is actually a terminus rather than a gateway," Armentano said. "The overwhelming majority never go on to use any drug harder than marijuana and most of those no longer use marijuana after the age of 25."
The findings have implications for drug policies, Armentano said. "The notion that we should continue to criminalize marijuana based on a false premise certainly needs to be reexamined," he said. However, he remained doubtful the findings would have much sway with president Bush's drug czar John Walters who was recently quoted as saying marijuana represented the nation's most serious drug problem. "If marijuana policy was driven by facts and science, we'd have a very different policy already," Armentano said.
Morral agreed his findings should be taken into account by legislators deciding on drug policies. He noted the Drug Enforcement Administration cites the gateway effect as one of the greatest harms of marijuana use on its Web site and "many policymakers have believed that. But our study proves that it's not a known harm and should be reevaluated," he said.
However, the RAND researchers said they do not think their findings support the legalization of marijuana. The gateway effect is just one of the harms associated with marijuana use, so disproving that effect still leaves other negative consequences of using the drug and does not imply it should be legalized, Morral said.
The White House's Office of National Drug Control Policy did not return phone calls from UPI by press time.