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Study Says Marijuana Alters Blood Flow in Brain

Marijuana users' problems with memory and concentration could be related to altered blood flow to the brain, according to new research from the National Institute on Drug Abuse.

The BBC reported Feb. 8 that long-term marijuana smokers could be risking memory damage and stroke because the drug appears to speed up blood flow in the brain, possibly because it causes abnormalities in small blood vessels. Marijuana use may narrow blood vessels, researchers said, and the effects linger even when users abstain for a month.

"In the long-term one might see cognitive difficulties, such as problems with memory and thinking," said lead researcher Dr. Ronald Herning.

The study looked at 54 marijuana users who smoked between two and 350 joints per week, as well as 18 nonsmokers. "Moderate" users -- those consuming 70 joints per week -- showed signs of normalizing blood flow after a month of abstinence. But "heavy" users -- those smoking up to 350 joints a week -- showed no improvement after a month of not smoking.

The research was published in the Feb. 8, 2005, issue of the journal Neurology.

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