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The war on weed
Newshawk: Peter Webster http://www.psychedelic-library.org/
Publication date: March 9, 2002
Source: New Scientist (UK)
Page: 6
Copyright: New Scientist, RBI Limited 2001
Contact: letters@newscientist.com
Website: http://www.newscientist.com/
Author: Kurt Kleiner
The war on weed
Controversy still rages over whether cannabis damages the brain
Do decades of dope-smoking wreck cannabis users' memory and concentration?
Or is this just another anti-marijuana myth?
This long-running debate reopened this week with the publication of a US
government-funded study which claims that smoking cannabis daily for 20
years or more impairs memory and attention. Its findings are contradicted
by others that have revealed no long-term effects.
The latest research involved 102 cannabis smokers in Seattle, Farmington in
Connecticut and Miami. Half had smoked for an average of 24 years. The
other half, described as "short-term" users, had smoked for 10 years on
average. Both groups reported smoking about two joints a day.
In tests such as memorising a list of 15 words, the long-term users
recalled 8.5 words on average, 2.5 fewer than both the short-term users and
31 non-users. The long-term users were also slower at mental arithmetic.
But in in other tasks, such as sorting cards, they were just as quick.
Both groups of users also tended to overestimate the time it took them to
complete a task, thinking it had taken them a third longer than it really had.
The authors conclude that cannabis has a cognitive effect that lasts beyond
the period of intoxication and that the longer you smoke, the worse the
effect on memory and attention. "We do not know exactly how that translates
into real-world problems, " admits team member Robert Stephens, a
psychologist at Virginia Polytechnic Institute and State University.
Nevertheless, he thinks long-term users might not function as well in
day-to-day life.
But there are other explanations for the results. For example, it was only
17 hours on average since the users had last smoked a joint, and some had
smoked just 12 hours earlier. Harrison Pope, a psychiatrist at Harvard
Medical School in Boston, says other studies, including one he published
last year comparing 108 users with 72 nonusers, reveal no long-term
effects. One difference, he says, is that his subjects were tested 28 days
after they had last smoked.
Pope also points out that the subjects in the latest study were all seeking
treatment for marijuana dependency, and might have had problems such as
anxiety or depression that affected their test scores.
Paul Armentano, director of research for the US National Organization for
the Reform of Marijuana Laws, is even less impressed by the results. "There
just doesn't seem to be a large cohort of people suffering these adverse
consequences," he says.
But even if long-term smokers who give up do not suffer any permanent
effects, Pope thinks continual heavy use does have an impact. "We've looked
at the lives of these people and how they function. They overwhelmingly
rated themselves as less effective and less happy than the control
subjects," he says.
More at: The Journal of the American Medical Association (vol 287, p 1123)
E-mail Kurt Kleiner
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Distributed without profit to those who have expressed a prior interest in
receiving the included information for research and educational purposes.
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