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US: Marijuana's Effects On Brain Are Reversible: Study

Reuters Health

Wednesday 17 Oct 2001

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NEW YORK (Reuters Health) - Intellectual impairment
associated with heavy marijuana use is apparently
reversible with abstinence, researchers report.

And marijuana withdrawal symptoms in habitual users
are similar to those seen with nicotine withdrawal,
according to a second report published in the October
issue of the Archives of General Psychiatry.

The lead author of the first report, Dr. Harrison G.
Pope, Jr. of McLean Hospital in Belmont, Massachusetts,
told Reuters Health, "It appears that cognitive
impairment from marijuana use is temporary and related
to the amount of marijuana that has been recently
smoked rather than permanent and related to an entire
lifetime consumption."

Pope and colleagues collected data on three groups of
marijuana users. One group consisted of 63 users who
had smoked marijuana at least 5,000 times in their
lives and were daily marijuana users.

In the second group, there were 45 former marijuana
users who had smoked marijuana at least 5,000 times
but had used it less than 12 times in the past 3
months. The third group was made up of 72 "controls"
who had not smoked marijuana more than 50 times.

People in the study abstained from marijuana for 28
days, during which time the researchers gave them tests
that assessed general intellectual function, abstract
thinking, sustained attention, verbal fluency and the
ability to learn and recall verbal and visuospatial
data. Tests were given at the beginning of the study
and on days 1, 7 and 28.

Heavy marijuana users had significantly lower scores
on word recall lists at the beginning of the study and
on the day 1 and day 7 tests compared with non-users.
However, by day 28 there were no significant differences
between the groups in any of the tests, with no
significant association between cumulative lifetime
marijuana use and test scores, Pope's group found.

"People who are regular heavy marijuana smokers will
exhibit some impairment that lasts days, and possibly
even a couple of weeks after they stop smoking--that's
the bad news. The good news is that if they abstain
from marijuana for longer than 4 weeks, then the
residual effects seem to disappear," Pope said.

In the second report, Dr. Alan J. Budney from the
University of Vermont in Burlington and colleagues
studied withdrawal effects in 12 daily marijuana
smokers.

"Comparing our results to studies of nicotine
withdrawal, it looks like the magnitude of the
severity of withdrawal is similar," Budney said in an
interview with Reuters Health. "So as people try to
quit smoking marijuana, one can expect them to have
problems with withdrawal."

The researchers had the study participants smoke
marijuana as usual for 5 days, then abstain for 3
days, smoke again for 5 days and abstain for
another 3 days.

Craving for marijuana, decreased appetite, sleep
difficulty and weight loss were more common in
abstaining periods. Aggression, anger, irritability,
restlessness and strange dreams were also
significantly increased during abstinence, Budney's
team found.

"This highlights the issue that when you treat
marijuana-dependent folk, they are going to complain
about withdrawal--it is real. If you consider tobacco
withdrawal real, you should consider marijuana
withdrawal real," Budney stressed.

SOURCE: Archives of General Psychiatry
2001;58:909-915, 917-924.


 

 

 

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