HIGH ROAD

MARIJUANA AS A "GATEWAY" DRUG

By the 1950s, Federal Bureau of Narcotics Commissioner Harry Anslinger
had backed away from his claim that marijuana turns people into
murderers. Instead he began arguing that it turns them into heroin
addicts. "Over 50 percent of those young addicts started on marijuana
smoking," Anslinger told a congressional committee in 1951. "They
started there and graduated to heroin; they took the needle when the
thrill of marijuana was gone."

Half a century later, this idea, known as the "gateway" or "stepping
stone" theory, remains a bulwark of marijuana prohibition. Its
durability is largely due to its ambiguity: Because it's rarely clear
what people mean when they say that pot smoking leads to the use of
"harder" drugs, the claim is difficult to disprove.

Survey data indicate that heroin and cocaine users generally use
marijuana first, and that people who try pot are much more likely than
people who don't to try other drugs. But there are several ways of
interpreting these facts. A recent study by the RAND Corporation's
Drug Policy Research Center, for example, found that a general
predisposition to use drugs, combined with a four-year lag between
access to marijuana and access to other illegal intoxicants, was
enough to account for the patterns observed in the government's surveys.

"The people who are predisposed to use drugs and have the opportunity
to use drugs are more likely than others to use both marijuana and
other drugs," said Andrew Morral, the lead author of the study, which
appeared in the December issue of the journal Addiction. "Marijuana
typically comes first because it is more available. Once we
incorporated these facts into our mathematical model of adolescent
drug use, we could explain all of the drug use associations that have
been cited as evidence of marijuana's gateway effect."

Case closed? Not quite. A study reported in this week's Journal of the
American Medical Association surveyed 311 pairs of Australian twins in
which one used marijuana by age 17 and one did not. The researchers
found that the early cannabis users were more likely than their twins
to use other drugs. They were four times as likely to use
psychedelics, three times as likely to use cocaine or other
stimulants, and more than twice as likely to use opioids.

These relative probabilities may sound impressive, but they're quite
modest compared to the numbers usually cited by defenders of the war
on drugs. The prohibitionist propaganda mill known as the Center on
Addiction and Substance Abuse, for example, trumpets the fact that
"12-to-17-year-olds who smoke marijuana are 85 times more likely to
use cocaine than those who do not." The results of the twin study
suggest that almost all of this difference is due to environmental and
personality factors, as indicated by RAND's analysis.

Even with twins, of course, there are differences in environment and
personality. The study's results were similar for monozygotic
("identical") and dizygotic ("fraternal") twins, which suggests that
genetic differences of the magnitude seen in siblings are not
important in determining who uses the "harder" drugs. But both kinds
of twins clearly differed in significant respects; otherwise, it would
not have been the case that one from each pair used marijuana early
while the other did not. If one twin happens to be less risk-averse or
more rebellious, or if he happens to have friends who know where to
get pot, that factor could explain both his early marijuana use and
his subsequent use of other drugs.

The researchers, for their part, speculated that the link between
early pot smoking and later drug use "may arise from the effects of
the peer and social context within which cannabis is used and
obtained. In particular, early access to and use of cannabis may
reduce perceived barriers against the use of other illegal drugs and
provide access to these drugs."

To expand on that point a bit, the government's decision to put
marijuana in the same category as cocaine and heroin may contribute to
a gateway effect in three ways:

1) Once teenagers break the law to try pot, they are less reluctant to
break the law to try other drugs.

2) Once they discover that the government has been lying about
marijuana, they are less inclined to believe official warnings about
other drugs.

3) Once they buy marijuana on the black market, they are more likely
to have the opportunity to buy other drugs.

A more obvious explanation for the connection between pot smoking and
other drug use is that people who discover that they like marijuana
may be more inclined to try other psychoactive substances, in the same
way that people who discover that they like bungee jumping may be more
inclined to try sky diving. You could say that bungee jumping is a
gateway to sky diving.

Notice that none of these interpretations involves a specific
pharmacological effect of the sort drug warriors seem to have in mind
when they suggest that pot smoking primes the brain for cocaine or
heroin. As a National Academy of Sciences panel observed in a 1999
report , "There is no evidence that marijuana serves as a stepping
stone on the basis of its particular drug effect." Last year the
Canadian Senate's Special Committee on Illegal Drugs likewise
concluded that "cannabis itself is not a cause of other drug use. In
this sense, we reject the gateway theory."

Of course, it all depends on which "sense" you have in mind. A few
years ago in the Drug Policy Analysis Bulletin, the social
psychologist Robert MacCoun laid out seven--count 'em, seven--different
versions of the gateway theory. "Given our current state of
knowledge," he concluded, "one can coherently argue that ( a ) the
gateway is a myth--it doesn't exist; ( b ) the gateway is very real and
it shows why we must sustain or strengthen our ban on marijuana, or
( c ) the gateway is very real and it shows why we should depenalize or
even legalize marijuana."

A theory that versatile will never die.