Marijuana Use May Restrict Blood Flow To The Brain [STUDY]

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A recent study links marijuana use with low blood flow to the brain, which may increase the risk for Alzheimer's disease. Marijuana also known as pot or weed is the most popular illegal drug worldwide and is recently gaining support for legalization for both recreational and medicinal purposes.

The study conducted by researchers at Amen Clinics looked at brain scans of 26,268 patients between the period of 1995 and 2005, at nine outpatient neuropsychiatric clinics across the United States. The patients had sought treatment of complex psychological or neurological problems.

The researchers discovered 982 patients in the database were diagnosed with cannabis use disorder and were found to have used marijuana so heavily that it affected their health, work and family life.

Brain scans of nearly 1,000 past and present marijuana users revealed abnormally low blood flow throughout their brains, compared to the control group of 92 people who had never used marijuana.

The study's lead researcher Dr. Daniel Amen, a psychiatrist and founder of the U.S. based Amen Clinics said "The differences were astonishing," as virtually every area of the brain measured was lower in blood flow and activity in the marijuana smokers than in the healthy group, according to Health News.

Compared to healthy group, the marijuana users had lower blood flow in the right hippocampus - an area that gets memories into long-term storage. The hippocampus distinguished healthy people from pot smokers better than any other area of the brain.

The researchers discovered that they could reliably distinguish the brains of marijuana users by checking blood flow to the hippocampus. Marijuana use is believed to interfere with memory formation by inhibiting the activities in the hippocampus.

The brain scans relied on a technology called single photon emission computed tomography (SPECT), normally used to track blood flow throughout the body.

"The growing lore in our country is that marijuana is innocuous, it is good medicine and it should be legalized," Amen said. "This research directly challenges that notion," according to Amen clinics.

However, 26 states and D.C. have legalized marijuana primarily for medical purposes. Amen noted that blood flow was reduced even in marijuana users who ingest the drug rather than smoke it,

Although, the study does not establish a direct "cause and effect" relationship, the authors concluded that doctors should reconsider recommending marijuana in the treatment of a patient diagnosed with Alzheimer's disease.

The findings thus raise a question about the impact of marijuana use on normal function in areas of the brain's important to memory and thinking, Maria Carrillo, chief science officer for the Alzheimer's Association says.

Carrillo added that sustained inadequate blood flow can damage and eventually kill cells anywhere in the body. The brain possess one of the  richest networks of blood vessels in the body which make it vulnerable.

The blood vessels transport nutrients to the brain and carry away waste, which is vital for normal cognitive function. A conclusion cannot be drawn from the study whether marijuana use increases a person's risk for cognitive decline or Alzheimer's disease.

However, other experts have raised concerns that the marijuana smokers who underwent the brain scans were already seeking treatment for psychiatric issues which could distort the result.

"It looks as if the cannabis users were all referred to the clinic for some problem while the healthy controls were not," said Mitch Earleywine, an advisory board member for NORML, which advocates for marijuana legalization. American Academy Neurologist Dr. Terry Fife of Phoenix, Ariz., agreed with Earleywine.

Fife said the study does not show the extent of the participants' marijuana use, outside of their diagnosis for cannabis use disorder. It is thus unclear how much of a user the participants were.

The possible link between marijuana and Alzheimer's disease will need further research, he said. The researchers published their findings in the Journal of Alzheimer's Disease.