Pubdate: Tue, 02 Apr 2002
Source: Ottawa Sun (CN ON)
Copyright: 2002, Canoe Limited Partnership
Contact:  http://www.fyiottawa.com/ottsun.shtml
Details: http://www.mapinc.org/media/329
Author: Helen Branswell
Bookmark: http://www.mapinc.org/pot.htm (Cannabis)

TOKERS' IQS UP IN SMOKE?

Heavy marijuana use lowers intelligence, Carleton University study finds

TORONTO (CP) -- It seems Hollywood isn't wrong when it portrays stoners as, 
well, dumb.

Heavy marijuana use does seem to drive down the IQ, by an average of four 
points, researchers from Carleton University report in today's issue of the 
Canadian Medical Association Journal.

The good news? The decline appears to right itself if the dope smoker butts 
out.

"A negative effect was not observed among subjects who had previously been 
heavy users but were no longer using the substance," the researchers wrote. 
"We conclude that marijuana does not have a long-term negative impact on 
global intelligence."

The issue of whether marijuana use has an impact on IQ is a contentious one.

'Controversial'

"It's been very controversial," said lead author Peter Fried of Carleton's 
psychology department. "There have been about 50 studies that have looked 
at the issue of if there's a residual effect and it's pretty much 50-50."

Resolving the issue has been tough, he said, because of the difficulty of 
coming up with before and after pictures of each subject's IQ.

About half the studies compared subjects' IQs while under the influence to 
their IQ after several days of enforced abstinence. But is a few days 
enough time to ensure the drug has cleared the system and all its 
neurological effects have worn off?

Fried and his colleagues had a neat answer to the problem. Since 1978, they 
have been following a group of children whose mothers -- some marijuana 
users, some not -- enrolled in the Ottawa Prenatal Prospective Study. These 
children are now aged 17-20.

To study the effect of marijuana on IQ, they studied a subset of 70 young 
adults, comparing current IQ scores to those on file from the subjects' 
pre-teen days.

Subjects were asked whether they used the drug and, if they did, whether 
their use was light or heavy. Urine samples were analyzed to ensure the 
subjects were being honest.

Nine of the subjects were light current users and another nine were former 
marijuana users who had smoked regularly in the past but hadn't used the 
drug for at least three months. Fifteen were heavy current users and 37 had 
never used the drug regularly.

Current heavy users showed a decline in IQ of 4.1 points, which is in the 
range of the decrease seen among children whose mothers drank three drinks 
of alcohol a day while pregnant or who used cocaine during their pregnancy. 
But the decrease was not seen among former heavy users.
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