SMOKING GRASS CAN, DUH . . .

Well, It Tends To Drive Down Your Iq. That's The Bad News. The Good News Is
The Decline Appears To Right Itself If The Dope Smoker Butts Out.

TORONTO -- 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 the latest 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.

"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 ages 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 a week); in contrast, the current heavy users had smoked, on
average, an estimated 2,386 joints over 3.1 years (mean of 14 joints a
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
functions.

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
recovery.

ON THE INTERNET

For more information, visit the Canadian Medical Association Journal
site: http://www.cma.ca/cmaj