HEY DUDE, WHERE'S MY IQ? TIME TO BUTT OUT

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
(www.cma.ca/cmaj). 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," 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.

Resolving the issue has been tough, said lead author Peter Fried of
Carleton's psychology department, because of the difficulty of coming up
with before and after pictures of each subject's IQ. 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.

Nine were light current users and another nine 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. Urine samples were analysed to ensure the subjects were
being honest about their marijuana use.

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.