Pubdate: Tue, 21 Mar 2006
Source: New York Times (NY)
Column: Vital Signs
Copyright: 2006 The New York Times Company
Author: Nicholas Bakalar
Bookmark: (Cannabis)



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. 
- ---
MAP posted-by: Richard Lake