AMERICAN
ACADEMY OF NEUROLOGY
Memory,
speed of thinking and other cognitive abilities get worse over time with
marijuana use, according to a new study published in the March 14, 2006, issue
of Neurology, the scientific journal of the American Academy of Neurology.
The study found that frequent marijuana users
performed worse than non-users on tests of cognitive abilities, including
divided attention (ability to pay attention to more than one stimulus at a
time) and verbal fluency (number of words generated within a time limit). Those
who had used marijuana for 10 years or more had more problems with their
thinking abilities than those who had used marijuana for five to 10 years. All
of the marijuana users were heavy users, which was defined as smoking four or
more joints per week.
"We found that the longer people used
marijuana, the more deterioration they had in these cognitive abilities,
especially in the ability to learn and remember new information," said
study author Lambros Messinis, PhD, of the Department of Neurology of the
University Hospital of Patras in Patras, Greece. "In several areas, their
abilities were significant enough to be considered impaired, with more
impairment in the longer-term users than the shorter-term users."
The study involved people ages 17 to 49 taking
part in a drug abuse treatment program in Athens, Greece. There were 20
long-term users, 20 shorter-term users and 24 control subjects who had used
marijuana at least once in their lives but not more than 20 times and not in
the past two years. Those who had used any other class of drugs, such as
cocaine or stimulants, during the past year or for more than three months
throughout their lives were not included in the study. Before the tests were
performed, all participants had to abstain from marijuana for at least 24
hours.
The marijuana users performed worse in several
cognitive domains, including delayed recall, recognition and executive
functions of the brain. For example, on a test measuring the ability to make
decisions, long-term users had 70 percent impaired performance, compared to 55
percent impaired performance for shorter-term users and 8 percent impaired
performance for non-users. In a test where participants needed to remember a
list of words that had been read to them earlier, the non-users remembered an
average of 12 out of 15 words, the shorter-term users remembered an average of
nine words and the long-term users remembered an average of seven words.
For more information on the effects of
marijuana use please contact the VB SAFE Coalition at 319-293-6412 or info@vbsafecoalition.com. For more information about the American
Academy of Neurology, visit www.aan.com.
