Pubdate: Wed, 22 Jan 2003
Source: Oklahoman, The (OK)
Copyright: 2003 The Oklahoma Publishing Co.
Contact:  http://www.oklahoman.com/
Details: http://www.mapinc.org/media/318
Author: Lindsey Tanner /AP Medical Writer

TWINS STUDY BOLSTERS POT 'GATEWAY THEORY'

CHICAGO - A study of Australian twins and marijuana bolsters the fiercely 
debated ``gateway theory'' that pot can lead to harder drugs. The 
researchers located 311 sets of same-sex twins in which only one twin had 
smoked marijuana before age 17. Early marijuana smokers were found to be up 
to five times more likely than their twins to move on to harder drugs.

They were about twice as likely to use opiates, which include heroin, and 
five times more likely to use hallucinogens, which include LSD.

Earlier studies on whether marijuana is a gateway drug reached conflicting 
conclusions. The impasse has complicated the debate over medical marijuana 
and decriminalization of pot.

Because this study involved twins, the findings would suggest that genetics 
play a subordinate role in drug use.

The study appears in Wednesday's Journal of the American Medical 
Association and was funded in part by the National Institutes of Health. It 
does not answer how marijuana, or cannabis, might lead to harder drugs.

``It is often implicitly assumed that using cannabis changes your brain or 
makes you crave other drugs,'' said lead researcher Michael Lynskey, ``but 
there are a number of other potential mechanisms, including access to 
drugs, willingness to break the law and likelihood of engaging in 
risk-taking behavior.''

Lynskey is a senior research fellow at Queensland Institute of Medical 
Research in Brisbane and a visiting assistant psychiatry professor at 
Washington University in St. Louis, where some of the research was done. 
Lynskey and colleagues acknowledged the study has several limitations, 
including relying on participants' reporting of their own experiences,

In an accompanying editorial, Denise Kandel of Columbia University's 
psychiatry department said the study does not explain ``whether or not a 
true causal link exists'' between marijuana and hard drugs.

``An argument can be made that even identical twins do not share the same 
environment during adolescence,'' she said.

Study participants were age 30 on average when they were asked about their 
teenage drug use. They included 136 sets of identical twins, who share the 
same genetic makeup.

About 46 percent of the early marijuana users reported that they later 
abused or became dependent on marijuana, and 43 percent had become 
dependent on alcohol.

Cocaine and other stimulants were the most commonly used harder drugs, 
tried by 48 percent of the early marijuana users, compared with 26 percent 
of the non-early marijuana users. Hallucinogens were the second most 
common, used by 35 percent of the early marijuana twins versus 18 percent 
of the others.
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MAP posted-by: Larry Stevens