Marijuana's So-Called Gateway Effect

April 5, 2002 -- Marijuana has been called a "gateway" drug because it's suspected that smoking pot is often the first step toward using stronger, potentially more dangerous substances. And now there's some proof to back up that suspicion.

The research appears in the most recent issue of Drug and Alcohol Dependence.

A Johns Hopkins University team looked at data from the 40,000 people age 21 and younger who took part in the National Household Survey on Drug Abuse. They found that 47% of those who used marijuana had been offered hallucinogenic drugs such as LSD, while only 6% of those who did not smoke pot had been offered hallucinogens. Overall, the pot smokers were at least 16 times more likely than were the nonsmokers to have had an opportunity to try hallucinogenic drugs.

Not only were the pot smokers more likely to get the chance to try the stronger drugs, but "marijuana use is associated with greater likelihood of actual hallucinogen use once an initial hallucinogen exposure opportunity has occurred," the researchers write.

They offer two possible explanations for the findings. First, kids using one drug are more likely to be hanging out with kids using other drugs. And second, once offered, kids who are already experimenting with drugs are more willing than non-users to try another.

The next step, the researchers write, is to clarify why some marijuana users are exposed to hallucinogens while others are not, and "to understand why some marijuana users do not progress [to other drugs] even when they have a chance to do so."