Marijuana Use Could Increase Alzheimer’s Risk: Study


Marijuana use may have a negative effect on a key memory center in the brain, says a new study that has researchers alarmed at the possible impact of cannabis use on cognitive health.

Using brain imaging technology to assess cognitive patterns in nearly 1,000 regular users of marijuana, researchers noted a significant reduction of blood flow in the patients’ hippocampus, a region of the brain associated with creating and storing new memories, when compared to people who don’t use marijuana.

Flickr Image Courtesy: Torben Hansen, CC BY-SA 2.0
Flickr Image Courtesy: Torben Hansen, CC BY-SA 2.0

The functioning of a person’s hippocampus has been linked to cognitive disorders, such as dementia and Alzheimer’s disease.

“The most predictive region distinguishing marijuana users from healthy controls, the hippocampus, is a key target of Alzheimer’s disease pathology. This study raises the possibility of deleterious brain effects of marijuana use,” report the study authors in the Journal of Alzheimer’s Disease.

The researchers used single photon emission computed tomography (SPECT) to map the brains of the study participants and discovered “abnormally low blood flow in virtually every area of the brain” among marijuana users. When analyzing the SPECT images, the study authors were essentially able to discern marijuana users from non-users based on how much blood flow the images showed.

“Low blood flow in the hippocampus in marijuana users reliably distinguished marijuana users from controls,” report the authors.

The new study comes as more areas of the country now allow marijuana use, and also follows new research linking cannabis to psychotic disorders. However, other studies have shown marijuana is helpful in easing substance abuse and depression.

“Open use of marijuana, through legalization, will reveal the wide range of marijuana’s benefits and threats to human health. This study indicates troubling effects on the hippocampus that may be the harbingers of brain damage,” said Dr. George Perry, editor in chief of the Journal of Alzheimer’s Disease.

Expanding a Needed Area of Research

The study sheds light on what the authors describe as an overlooked area of medical research. “Few studies have evaluated the impact of marijuana use on regional cerebral blood flow,” they write.

Yet the health impact – on cognition and the brain, in particular – remains a serious question as more people use marijuana.

“As a physician who routinely sees marijuana users, what struck me was not only the global reduction in blood flow in the marijuana users’ brains, but that the hippocampus was the most affected region due to its role in memory and Alzheimer’s disease,” said Elisabeth Jorandby, M.D., a co-author of the study.

“This work suggests that marijuana use has damaging influences in the brain – particularly regions important in memory and learning and known to be affected by Alzheimer’s,” added Jorandby.

At this time, the researchers advise additional studies to help the medical community gain a greater understanding of the effects of ongoing marijuana use.

“Our research demonstrates that marijuana can have significant negative effects on brain function. The media has given the general impression that marijuana is a safe recreational drug; this research directly challenges that notion. In another new study just released, researchers showed that marijuana use tripled the risk of psychosis. Caution is clearly in order,” said co-author Daniel Amen, M.D.