Marijuana Use Affects Blood Flow In Brain Even After
\ST. PAUL, Minn.
People who smoked marijuana had changes in the blood
flow in their brains even after a month of not
smoking, according to a study published in the
February 8 issue of Neurology, the scientific
journal of the American Academy of Neurology.
The findings could explain in part the problems with
thinking or remembering found in other studies of
marijuana users, according to study authors Ronald
Herning, PhD, and Jean Lud Cadet, MD, of the
National Institute on Drug Abuse in Baltimore, Md.
The study involved 54 marijuana users and 18 control
subjects. The marijuana users volunteered to take
part in a month-long inpatient program. The blood
flow velocity in brain arteries was tested with
transcranial Doppler sonography in all participants
at the beginning of the study and again at the end
of the month for the marijuana users.
The blood flow velocity was significantly higher in
the marijuana users than in the control subjects,
both at the beginning of the study and after a month
of abstinence from marijuana use. The marijuana
users also had higher values on the pulsatility
index (PI), which measures the amount of resistance
to blood flow. This is thought to be due to
narrowing of the blood vessels that occurs when the
circulation system's ability to regulate itself is
"The marijuana users had PI values that were
somewhat higher than those of people with chronic
high blood pressure and diabetes," Herning said.
"However, their values were lower than those of
people with dementia. This suggests that marijuana
use leads to abnormalities in the small blood
vessels in the brain, because similar PI values have
been seen in other diseases that affect the small
The PI values for light and moderate marijuana users
improved over the month of abstinence. There was no
improvement for heavy marijuana users. The light
users smoked two to 15 joints per week. The moderate
users smoked 17 to 70 joints per week, and the heavy
users smoked 78 to 350
joints per week.
The American Academy of Neurology, an association of
more than 18,000 neurologists and neuroscience
professionals, is dedicated to improving patient
care through education and research. A neurologist
is a doctor with specialized training in diagnosing,
treating and managing disorders
of the brain and nervous system such as stroke,
Alzheimer's disease, epilepsy, Parkinson's disease,
and multiple sclerosis.
For more information about the American Academy of
Neurology, visit its Website at
Note: This story has been adapted from a news
release issued by American Academy Of Neurology.