HTTP/1.0 200 OK Content-Type: text/html Dope, After All, Appears To Be An Appropriate Name
Pubdate: Tue, 02 Apr 2002
Source: Halifax Herald (CN NS)
Copyright: 2002 The Halifax Herald Limited
Author: Helen Branswell, The Canadian Press
Bookmark: (Cannabis - Canada)


Heavy Marijuana Use Lowers IQ, but Only Temporarily, Study Finds

Toronto - It seems Hollywood isn't wrong when it portrays stoners as, well, 

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

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

"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.

"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 to 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.

"We had the unique opportunity, because of our long-term study, to have IQ 
measures on these kids before they ever knew the word marijuana," Fried 
said from Ottawa.

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

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 
were non-users who had never used the drug on a regular basis.

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.

"This lack of a negative impact among the former heavy users is striking as 
they smoked, on average, an estimated 5,793 joints over 3.2 years (mean of 
37 joints per week); in contrast, the current heavy users had smoked, on 
average, an estimated 2,386 joints over 3.1 years (mean of 14 joints per 
week)," the article said.

"Certainly in a low-risk sample - that's another thing to emphasize - which 
these young adults are, it does look like the deficit in IQ, if the people 
stay clean for three months or so is recoverable," Fried added.

While the results are positive news for recreational marijuana users, he 
cautioned the findings are preliminary. His team is still studying the 
subjects to see if there is any impact on attention, memory or other mental 

As well, it's not clear the findings can be generalized across the full 
spectrum of marijuana users. These subjects are middle class with 
above-average intelligence, kids who don't regularly use other drugs and 
who are well nourished. The drug's long-term impact might not be the same 
on someone with a riskier lifestyle, Fried said.

"In the real world out there of course the heavy users probably are 
poly-drug users, etc. And they may be at a greater risk and their IQ may 
not recover."

Furthermore, Fried said it would be a leap to conclude that because IQ 
recovers in young adults who have used marijuana for a few years, 40- and 
50-year olds who've been smoking dope for decades can count on the same 
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