Marijuana use alters blood flow

Marijuana users have faster blood flow in their brains, even after a month of not smoking, than nonusers, researchers have found.

The study suggests that marijuana users have narrowed arteries, similar to patients with high blood pressure and dementia, and could help explain reports that heavy marijuana users have trouble on memory tests, said the researchers at the National Institute on Drug Abuse in Baltimore.

Ronald Herning and Jean Lud Cadet tested 18 nonsmokers and 54 marijuana users who smoked at least two joints a week. They used Doppler sonograms to measure blood flow in volunteers’ brains at the beginning of the study and a month later, after everyone agreed to abstain from marijuana for four weeks.

The smokers had faster blood flow, both at the start and after a month of abstinence, Herning and Cadet reported in the February issue of the journal Neurology.