Marijuana Users Suffer Lower Blood Flow to the Brain than Non-Users

Technician is examining blood flow of a patient

In a 2016 press release, a specialist with the Journal of Alzheimer’s Disease warned that “Researchers … demonstrated abnormally low blood flow in virtually every area of the brain studies in nearly 1,000 marijuana compared to healthy controls, including areas known to be affected by Alzheimer’s pathology such as the hippocampus.” That writer pointed out how, as the U.S. races to legalize marijuana for medicinal and recreational uses, the findings regarding marijuana consumption and blood flow to the brain should serve as a cautionary tale for pro-legalization advocates. If cannabis is legalized without the broader public being aware of its harmful effects, users could suffer serious, long-term harm.

Marijuana Users Have Lower Blood Flow to the Brain

A group of researchers obtained brain scan data from 26,268 people, scans that had been recorded from patients across the country between 1995 and 2015. The researchers used single photon emission computed tomography (SPECT). This sophisticated imaging study evaluates blood flow and activity patterns to analyze blood flow levels across the brain in cannabis users and non-users. The findings showed cannabis users had significantly lower blood flow, especially in the brain’s key memory and learning centers.

“Our research has proven that marijuana users have lower cerebral blood flow than non-users. This work suggests that marijuana use has damaging influences in the brain...”

The data is hard evidence for why long-term cannabis users sometimes develop memory loss and a drop in IQ over time. One of the study’s co-authors, Elisabeth Jorandby, M.D., spoke to this point. “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,” she said. “Our research has proven that marijuana users have lower cerebral blood flow than non-users. 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.” The researchers plan to further investigate what they believe to be a link between cannabis consumption and Alzheimer’s.

Other authors and researchers involved in the study showed concern that not enough is being done to properly inform the public about the risks of marijuana as the drug is rapidly legalized across America. According to Daniel Amen, M.D., “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, researchers showed that marijuana use tripled the risk of psychosis. Caution is clearly in order.” The other study Dr. Amen referred to is a 2016 work that connected heavy and regular marijuana consumption with a 300% increase in risk for psychotic episodes, which can recur and reappear even after the individual ceases marijuana use.

Marijuana Has Other Harmful Effects Too


The findings connecting cannabis consumption to reduced blood flow and oxygen levels in the brain are recent, but there is longstanding evidence that cannabis has adverse effects on users. People who use cannabis may experience unwanted symptoms like:

  • Changes in mood and emotion
  • Altered sense of the passage of time
  • Delusions (when cannabis is taken in high doses)
  • Hallucinations (when cannabis is taken in high doses)
  • Impaired body movement, difficulty in ambulatory control
  • Impaired memory, including the risk of long-term memory loss
  • Difficulty with thinking, problem-solving, and reduced cognitive function
  • Psychosis (the risk for this is highest with regular use of high-potency marijuana)
  • Altered physical senses (for example, seeing different colors or shapes being blurry and indistinct)

Cannabis can have serious long-term effects on users, especially when someone begins using it as a teenager. For example, heavy cannabis use in one’s youth can lead to impairments in thinking, memory, and learning functions, and it can affect how the brain builds connections between the areas of the brain necessary for these functions. One study from New Zealand found that people who use cannabis in their youth lose an average of 8 IQ points, with no indication of the IQ returning after they cease drug use.

Cannabis is Addictive. Those Who Can’t Stop Using It Should Seek Professional Help.

According to the National Institute on Drug Abuse, marijuana is the second most frequently cited drug at addiction treatment center admissions, second only to alcohol and alcohol combined with other drugs. About 17% of people seeking help for addiction say their drug of choice is cannabis.

It’s time to dispel the myth that marijuana cannot be addictive. It can be, and when people become hooked on it, they’ll need professional help to get clean. If you know someone who’s using cannabis and can’t stop using it alone, please get in touch with a qualified residential drug and alcohol rehab center as soon as possible, and help them enter that facility. Please don’t wait until it is too late and they suffer long-term harm from using cannabis.

Sources Cited:

  • JAD. “New Study Shows Marijuana Users Have Low Blood Flow to the Brain.” Journal of Alzheimer’s Disease, 2016.
  • UPI. “Cannabis abuse triples risk of psychosis: Study.” United Press International, 2016.
  • NIDA. “Cannabis (Marijuana) DrugFacts.” National Institute on Drug Abuse, 2019.
  • NIDA. “DrugFacts.” National Institute on Drug Abuse, 2011.



After working in addiction treatment for several years, Ren now travels the country, studying drug trends and writing about addiction in our society. Ren is focused on using his skill as an author and counselor to promote recovery and effective solutions to the drug crisis. Connect with Ren on LinkedIn.