Sept. 2, 2010 -- New research finds little support for the hypothesis that marijuana is a "gateway" drug leading to the use of harder drugs in adulthood.
Teens in the study who smoked marijuana were more likely to go on to use harder illicit drugs, but the gateway effect was lessened by the age of 21, investigators say.
The study is published in the September issue of the Journal of Health and Social Behavior.
Failure to graduate from high school or find a job were all bigger predictors of drug use in young adulthood than marijuana use during adolescence, says study researcher Karen Van Gundy, who is a sociologist at the University of New Hampshire.
She adds that the findings have implications for policymakers on the front lines in the war on drugs.
"If we overly criminalize behaviors like marijuana use among teens, this could interfere with opportunities for education and employment later on, which, in turn, could be creating more drug use," she tells WebMD.
Marijuana's Gateway Effect Goes Away
Van Gundy says she did not set out to disprove the idea that marijuana is a gateway drug when she and co-researcher Cesar J. Rebellon examined survey data from 1,300 mostly male Hispanic, white, and African-American young adults who attended south Florida public schools in the 1990s. The participants were followed from enrollment in the sixth or seventh grade until they reached their late teens or early 20s.
"Most of the previous research has examined early drug use among people with serious drug problems," she says. "These people do tend to progress from alcohol and marijuana use to other drugs."
When the teens in the study were followed forward into young adulthood, however, a different picture emerged.
"We were somewhat surprised to find the gateway effect wasn't that strong during the transition to adulthood," Van Gundy says. "It really didn't matter if someone used marijuana or not as a teen."
Specifically, the study found illicit drug abuse in young adulthood to be much more closely linked to stress during the teen years and whether or not the young adults were employed.
"Assuming and occupying conventional roles, such as 'worker,' may close the marijuana gateway by modifying and redirecting substance use trajectories," the researchers write.
The Fight Against Drugs
The findings suggest anti-drug efforts aimed at keeping kids in school and providing employment opportunities may have the biggest positive impact on drug use in adulthood, Van Gundy says.
Urban sociologist and drug-use researcher Lesley Reid agrees.
An associate professor of sociology at Georgia State University in Atlanta, Reid's research has focused on the gateway effect of so-called club drugs like ecstasy and cocaine among heavy drug users in their 20s.
She says most of these heavy users do start with alcohol and marijuana and progress to harder drugs.
"Obviously, we don't see this age effect among these heavy users," she tells WebMD. "But in the general population most people do outgrow behaviors like drug use and other delinquent behaviors."
'Gateway' Pioneer Critical of Study
But Columbia University sociologist Denise B. Kandel, PhD, whose research early in the decade found marijuana to be a gateway drug, calls the new research highly flawed and the conclusions "ill founded."
She tells WebMD that the design of the study did not allow the researchers to properly test the hypothesis that marijuana is a gateway drug.
Kandel does not disagree with the conclusion that social position in young adulthood plays a big role in drug use during this time. But she says the researchers fail to consider the potential impact of early marijuana use on social position.
"Using marijuana as a teen can certainly have an impact on whether or not someone fails to graduate from high school or gets a job," she says. "And this increases the risk of persistent illicit drug use."