Behavior:

MARIJUANA AND A SLOWER MIND AND BODY

Long-term heavy users of marijuana perform significantly worse on
tests of mental agility and physical dexterity than short-term users
or nonusers, even when they have abstained from smoking for more than
24 hours, new research shows.

Scientists, led by Lambros Messinis, a neuropsychologist at
University Hospital in Petras, Greece, tested three groups.

They were 20 long-term users who had smoked four or more marijuana
cigarettes a week for at least 10 years, 20 short-term users who had
smoked a similar amount for 5 to 10 years and, finally, 24 people,
representing a control group, who had used marijuana no more than 20
times in their lives and not in the prior two years.

The long- and short-term users were drawn from participants in a drug
rehabilitation program.

Even after controlling for I.Q., other drug use, age, sex, depression
and other variables, long-term users scored significantly lower than
control group members and shorter-term users on tests of verbal
fluency, memory and coordination.

The exercises included naming objects when shown pictures of them,
thinking up words with the same initial letter, listening to lists of
words and later recalling them and drawing lines in the proper order
among numbers and letters randomly spread on paper.

The study appears in the March issue of Neurology.

Dr. Messinis acknowledged that the results might have differed with
marijuana users from the general population. Still, he said, the
study was carefully controlled, and frequent heavy use appeared to
have significant negative effects on performance.