Top Menu

Imaging Scans Show Daily Marijuana Use Can Have Negative Effect on Brain


Imaging scans of the brains of people who smoke marijuana daily show a decrease in the number of receptors involved in pleasure, appetite, pain tolerance and many other key mental and bodily functions, a new study shows.

The study, presented at the Society of Nuclear Medicine Annual Meeting, included 30 chronic daily marijuana smokers. They were monitored at an inpatient facility for four weeks. Their brains were scanned using positron emission tomography (PET). The study found certain receptors in the brains of marijuana smokers were decreased by about 20 percent compared with people who had a limited lifetime exposure to marijuana, also known as cannabis. “With this study, we were able to show for the first time that people who abuse cannabis have abnormalities of the cannabinoid receptors in the brain,” lead researcher Dr. Jussi Hirvonen said in a news release.

The researchers then re-scanned the brains of 14 of the marijuana users who had abstained from smoking marijuana for one month and found a marked increase in the brain receptors compared with the beginning of the study, HealthDay reports. The researchers say the findings suggest that the damaging effects of marijuana use are reversible.

The study was a collaboration between the U.S. National Institute of Mental Health and U.S. National Institute on Drug Abuse.

9 Responses to this article

  1. Avatar of Leah Caso
    Leah Caso / November 28, 2012 at 8:55 pm

    Any study produced by the us government is propaganda. I’d like to see similar studies produced from another source.

  2. Avatar of wow just wow
    wow just wow / May 2, 2012 at 4:13 pm

    Why is it that opponents for pot simply refuse to accept the huge and still-growing mountain of research (or evidence, if you prefer) that pot is indeed beneficial? that it cures cancer ? the only reason its illegal is competition from other big industries, this is common knowledge and you have your heads in the sand. You cannot ignore the millions of law abiding responsible people that enjoy marijuana for all its wonderful qualities. If you want to answer some of your own questions about pot (you must have many being so uninformed) watch ‘What if pot cured cancer” but im sure you wont because you dont want it to cure anything, like the drug war profiteers. PWNED xD

  3. Avatar of Frank Winkler
    Frank Winkler / June 14, 2011 at 4:59 pm

    Why is it that proponents for pot simply refuse to accept the huge and still-growing mountain of research (or evidence, if you prefer) that pot is indeed harmful, however much they otherwise enjoy indulging in its use. There are no revelations here that have not been demonstrated time and again globally, yet denial persists. Is it any wonder that we continue to see abusers who have suffered damage and now require treatment/ assistance? A thousand refutations can not change proven fact.

  4. Ben House / June 10, 2011 at 9:22 pm

    I am with Doug, seeking information that helps. What does reduction in these receptors do? From what I hear it increases appetite, reduces pain and feels good. I very much look forward to the information Join Together has provided, but would ask you screen and give us something helpful. I have seen some of Dan Amen’s scan work and his descriptions of the effects gave me information that made sense and was useful.

  5. Brinna Nanda / June 10, 2011 at 8:18 pm

    “More money has been spent trying to find something wrong with cannabis than has been spent on any other drug, and the findings are woeful… there is just no support for the idea that cannabis is anything other than benign as a drug can be.” ~ Terence McKenna

  6. Avatar of Doug Moser
    Doug Moser / June 9, 2011 at 5:08 pm

    Call me a watchdog amateur science writer. The JT headline speaks of the possible hazards of “daily [marijuana] use” use, while the SNM headline is a bit more specific, calling it “chronic” use. The SNM press release goes on to say, “…while chronic cannabis smoking causes downregulation of CB1 receptors, the damage is reversible with abstinence.” Given our “zero tolerance, abstinence-only” culture/profession, it goes to say that said damage could also be reversed (albeit more slowly) with harm reduction. Though it was made clear that the subjects smoked “daily” (we can reasonably guess what that means), what is “chronic marijuana use?” What defines “chronic…heavy smokers” or “abusers?” Why not tell us? Regarding the reduction in CB1 receptor sites, “These changes were found to have a correlation with the number of years subjects had smoked.” How many years WAS that? Five? Thirty-five? How come the writers — and/or the researchers — include certain specifics (“radioligand, 18F-FMPEP-d2… is a combination of a radioactive fluorine isotope and a neurotransmitter analog…” without telling us these other bits of information?!?! This reader can handle a bit of complexity! Some of us might even be capable of drawing our own conclusions (how dare us!). Do we really need to “rally around the research” (or a cause) THAT bad?

  7. Avatar of Gary
    Gary / June 24, 2011 at 3:35 pm

    Frank I am with you on this one. As a former pothead and present CD therapist, the information about the harmful effects of cannabis has been there for a long time. The denial factor with cannabis users and supporters is the highest of any drug I see, especially when I teach classes on cannabis. Even with the information about how long THC stays in the system, the increase in cell walls width in the brain and the effect on cognition and learning, the possibility of psychotic breaks among long term users, people still think of it as a non-habit forming, no harm drug. In my own experience, I quit back in 1982 because of the social phobia, paranoya and other effects I had from 20 year use of this drug, and that was when the THC level was a lot lower than now. But it surely is hard to convince some people about how dangerous the drug is.

  8. Avatar of ithalia77
    ithalia77 / January 17, 2012 at 9:40 pm

    To Gary and Frank… Yes, Marijuana is harmful but I find it hard to believe that the damage and detriment of its use come anywhere near to touching a drug that is in mainstream use by nearly all Americans. This drug has caused diseases, domestic violence, loss of career and family, loss of life, incarceration and violent death. Can you guess what this drug may be???= ALCOHOL. And I do believe that this also kills brain cells as well. By the way, no, I am not a pot smoker (nor user of any other type of drug) and I am a very light drinker. Just thought I would share my thoughts …you may agree or disagree.

  9. Avatar of Joe
    Joe / March 2, 2013 at 10:41 pm

    “Cell walls” on neurons? Who knew?

Leave a Reply

Please read our comment policy and guidelines before you submit a comment. Your email address will not be published. Thank you for visiting

four − = 2

Reproduction in whole or in part of this publication is strictly prohibited without prior consent. Photographic rights remain the property of Join Together and the Partnership for Drug-Free Kids. For reproduction inquiries, please e-mail