Study: Marijuana Use Not Associated With Previously Reported Changes In Brain Morphology

  • by Paul Armentano, NORML Deputy Director February 10, 2015

    Study: Marijuana Use Not Associated With Previously Reported Changes In Brain MorphologyIt was less than a year ago when the mainstream media was chock-full of headlines like this one: ‘Brain changes associated with casual marijuana use in young adults, study finds.’ The alarmist headlines were in response to a controversial paper published by researchers at Harvard University in Boston and Northwestern University in Chicago which alleged to have found differences in brain morphology in a cohort of 20 college-age marijuana users as compared to 20 non-users. The study’s investigators attributed the differences to subjects’ cannabis use.

    But a funny thing happened when a team of scientists from the University of Colorado and the University of Kentucky tried to replicate these results in a separate, larger sample (158 participants) of subjects after rigorously controlling for both groups’ use of alcohol.

    They couldn’t.

    Writing in the January 28 edition of The Journal of Neuroscience, authors summarized:

    “[T]his retrospective study examined brain morphology in a sample of adult daily marijuana users (n = 29) versus nonusers (n = 29) and a sample of adolescent daily users (n = 50) versus nonusers (n = 50). Groups were matched on a critical confounding variable, alcohol use, to a far greater degree than in previously published studies.

    We acquired high-resolution MRI scans, and investigated group differences in gray matter using voxel-based morphometry, surface-based morphometry, and shape analysis in structures suggested to be associated with marijuana use, as follows: the nucleus accumbens, amygdala, hippocampus, and cerebellum.

    No statistically significant differences were found between daily users and nonusers on volume or shape in the regions of interest. Effect sizes suggest that the failure to find differences was not due to a lack of statistical power, but rather was due to the lack of even a modest effect.”

    Why the contradictory results? Investigators speculated that previously reported imaging studies failed to adequately control for the impact of alcohol, a substance that “unlike marijuana, … has been unequivocally associated with deleterious effects on brain morphology and cognition in both adults and adolescents.” In other words, researchers theorized that previously reported differences in the brain images of marijuana consumers as compared to non-users were likely because of subjects consumption of booze, not cannabis.

    They concluded, “In sum, the results indicate that, when carefully controlling for alcohol use, gender, age, and other variables, there is no association between marijuana use and standard volumetric or shape measurements of subcortical structures. … [I]t seems unlikely that marijuana use has the same level of long-term deleterious effects on brain morphology as other drugs like alcohol. The press may not cite studies that do not find sensational effects, but these studies are still extremely important.”

    An abstract of the study, “Daily Marijuana Use Is Not Associated with Brain Morphometric Measures in Adolescents or Adults,” is online here.

    34 responses to “Study: Marijuana Use Not Associated With Previously Reported Changes In Brain Morphology”

    1. fireweed says:

      that and there’s evidence that it protects against Alzheimer’s,and now the evidence is out that it has protective properties against a whole host of inflammatory-process diseases like cancer, diabetes, arthritis. In fact, it’s starting to look like we all should be smoking a little hooch.

      it’ll be interesting to see 10 years down the road if there is an inverse correlation between regular cannabis consumption and these inflammatory diseases.

    2. Anonymous says:

      Aw, too bad for the prohibitionists.

    3. Dave Evans says:

      “To say that cannabis is in no way related to alcohol is a led zeppelin at NORML.”

      Do you folks see how insidious propaganda can be? Even NORML has mentally blended marijuana and alcohol together. Even though they know it is not, the mental association is too strong between partying and drinking and smoking marijuana is too strong for people to make good sense of what they see; apparently. I don’t really know what to make of these kinds of mental tricks we play on ourselves.

      NORML, that shouldn’t be a lead zeppelin; it should be obvious!

      The bad effects of alcohol and tobacco keep being dumped at marijuana’s feet and it is beyond stupid.

      [Editor’s note: Alcohol and cannabis are self-evidently not the same. But, both drugs cause impairment, therefore standards of impairment and accurate testing for such re cannabis is not only coming, but has been invited by NORML (and all of the other drug policy reform groups) for decades.]

    4. Julian says:

      Ha! Haaaa! Universities in pro cannabis states are being funded for authentic scientific studies! And with time to spare! Judge Mueller still has not made her decision. If studies keep pouring out at this rate, take your TIME Judge! We can wait a few more weeks for your decision!

    5. Galileo Galilei says:

      Irreproducible results! Yet prohibitionists like Dr. Andrew Harris will cite the changes-in-brain-morphology study for decades to come.

      HINT: If your physician is treating you based on irreproducible, 30-year-old studies, find a new physician.

    6. Mike Schärer says:

      A question I have pertaining the study mentioned:
      They used a control group which did not use Cannabis for the last 60 days. People from that group could therefore have used it in the past. (see section Materials and Methods for details) If Cannabis was associated with irreversible brain alterations it could be that no changes were found because the control group already had irreversibly altered brain structure..Why did they not use a control group which had not used Cannabis at all?

      M. Schärer

    7. Todd says:

      These Journal of Neuroscience level scientists assume that the brain is a story telling data processor that can be hurt by marijuana. Would your mind fit in a small mechanical box? No, so don’t claim you can MRI a thought or idea in high resolution and then tell us weed “has been unequivocally associated with deleterious effects on brain morphology and cognition in both adults and adolescents”.

      [Paul Armentano responds: “so don’t claim you can MRI a thought or idea in high resolution and then tell us weed “has been unequivocally associated with deleterious effects on brain morphology and cognition in both adults and adolescents”. The study’s authors said just the opposite.]

    8. andy arevalol says:

      do you think mary j should be legalized in every state

    9. bob says:

      I am a firm believer in puff puff pass and this study does appear to be much more scientific BUT….regardless of any studies think that use of any substance by teens in their developmental years is a bad idea….19 maybe 20 or so do as you please but moderation is always a good idea

    10. Julian says:

      It occurs to me that the research revenue has increased greatly in pro-cannabis states such as those mentioned in this study from the Universities of Kentucky and Colorado. Hemp Hats off to the brave students and faculty involved in this vital research.
      The money trails from prohibition have deep roots, but they’re not as strong as they used to be. I just heard an NPR report about wealthy investors using Canada’s banking system to get loans to create enormous indoor grow operations just north of Washington state. Just think, Congress; All that money going to Canada, preventing violence with herbal medicine, because we’d rather spend more on law enforcement ? All those lights and electricity to power a small village when we could be growing hemp right under the Kentucky sun and creating jobs without spending a dime… And this is the Congress that’s all about “cutting spending?” How about cutting subsidies from pharmacuetical companies taking jobs out of the country to sell us poison when we could be subsidizing medicinal marijuana with the revenue from growing industrial hemp and recreational marijuana… and creating sustainable career JOBS right here in the U.S. Of A?!
      …oh wait; must be that encaphalitis again… That’s alright, I’ve gotta cure for that…