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.