Pubdate: Tue, 02 Apr 2002
Source: Minneapolis Star-Tribune (MN)
Copyright: 2002 Star Tribune
Author: Andre Picard (Toronto Globe and Mail)
Bookmark: (Cannabis)


Smoking pot may leave you stoned, but it apparently won't make you stupid.

Researchers at Carleton University in Ottawa have found that people who 
smoke moderate amounts of marijuana, even over a number of years, do not 
experience decreases in IQ.

And while the IQ of current heavy smokers (more than five joints a week) 
dips slightly, those losses do not seem to last over time. Former pot 
smokers, no matter their intake, show no long-term decreases in 
intelligence quotient.

"Marijuana does not have a long-term negative impact on global 
intelligence," said Peter Fried, a professor of psychology at Carleton 

He cautioned, however, that more research is required to determine whether 
smoking pot affects specific intelligence functions such as short-term 
memory and attention span.

"I don't want people to read this and think there are no long-term effects 
from smoking pot," Fried said.

The new study, published in the current edition of the Canadian Medical 
Association Journal, is one of the first to look at the long-term impacts 
of marijuana on young people who could be examined before and after they 
took up the habit.

Fried is director of the Ottawa Prenatal Prospective Study, which, since 
1978, has followed a group of people from birth onward. Their IQ was tested 
at ages 9 to 12, and again at ages 17 to 20. For this aspect of the 
research, a group of 74 subjects were questioned about marijuana use, and 
urine tests were conducted to test for the presence of cannabinoids.

As preteens, the group had a mean IQ score of 113.8, and it rose to 116.4 
as adults. Among light users of marijuana, scores rose almost six points in 
that period, while among heavy smokers, scores fell by four points. Among 
former users, IQ rose 3.5 points, regardless of previous levels of 
marijuana use.

"A four-point drop in IQ may not seem large for an individual, but it is 
significant in a group," said Fried, expressing concern about excessive use.

He said he was surprised both at how many young people smoked marijuana and 
the quantities ingested. Almost half had smoked pot. That is considerably 
higher than a larger survey conducted by the Center for Addiction and 
Mental Health in Toronto, which found that 29.2 per cent of teens smoke 
marijuana and 28.3 per cent smoke cigarettes.

In the new study, more than one in five of the young people smoked 
marijuana heavily - more than five joints weekly, with an average of 14 
joints a week. But surprisingly, the former heavy users - 37 joints weekly 
on average - did not seem to suffer intelligence impairment.

Fried added, however, that the majority said they quit because they were 
suffering from short-term memory loss and concentration problems.

The psychologist said the results of his research are preliminary, but he 
published them in direct response to an editorial in the Canadian Medical 
Association Journal that advocated decriminalization of marijuana, saying 
research shows "minimal negative health effects with moderate use."

The journal said the penalty for marijuana possession should be similar to 
a parking infraction.

Fried said that while he agrees laws need to be changed, he is worried that 
the debate has been grossly oversimplified. "You can't just say, 
holus-bolus, that the drug is innocuous. Despite widespread use, there are 
huge gaps in our knowledge."
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