Harvard’s Madras Critiques University of Pittsburgh Marijuana Study


Bertha Madras, professor of psychobiology at Harvard Medical School, has printed a critique listing 20 flaws to a recent study finding no differences in physical or mental health problems between users and non-users of marijuana. 

The long-term marijuana use study led by Jordan Bechtold, of the University of Pittsburgh School of Medicine, was published earlier this month in the Journal of Psychology of Addictive Behaviors.  Bechtold et al., followed 408 participants for over 20 years and found no association between marijuana use at a young age and an increased risk of psychosis, depression, and anxiety in adulthood.

See MIA’s coverage of Bechtold’s study here →

Madras writes:

“A critical evaluation of the validity of the findings and sweeping conclusions is essential, lest they are interpreted inappropriately. A perusal of the study and the authors’ stated caveats in the manuscript reveal significant weaknesses, with the use of an unrepresentative, possible archaic population, inadequate sample size, inadequate methodologies to assess mental health and physical problems, (self-reports, evaluation of psychiatric status without considering the “spectrum” nature of psychiatric conditions, and absence of addiction evaluation). The findings conflict with other well designed longitudinal studies that assess long-term consequences of marijuana use with early age of initiation of marijuana.”

See Madras’ full response here →


  1. Checked out the “rebuttal,” its bias and agenda are apparent; plus it’s like listening to witch doctors and theologists pontificating over nebulous concepts such as ether, demonic possession, schizophrenia and other archaic mythological notions. What’s the use in arguing?

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    • This rebuttal is nothing but a bias attack on a legitimate study. All the problems she brought up can be compared to every single other longitudinal study as well. She is arguing that the size of the sample used is too small, but compares it to cross sectional studies which can support a larger sample size. Trying to get a longitudinal study with the sample size she suggested of 10,000 participants would be close to impossible. She comments on how the outcomes were self reporting. Even the questionnaires she mentioned that diagnose mental health disorders are practically self reporting. Sorry we can’t stick someone with a needle, measure their shoe size and declare someone 100% addicted to Cannabis, or even that it is detrimental to their overall health. self reporting is the best we got right now. Also “Marijuana potency was far lower (1980’s to 1990’s) during the period of marijuana consumption of this population. This conceivably affects outcomes and consequences.” Source please; or is that your own personal opinion?

      Now this rebuttal does bring up some good ideas and we shouldn’t attack this person just for having a different idea. We can take her ideas to heart, and use them to prove her wrong. With the next study there should be medical evals from doctors, a control group, and a larger sample. Haters gonna Hate

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  2. The interesting thing is that cannabis has been used for thousands of years and only came into disrepute in the time of Nixon and his cronies. And of course, dear Ronnie furthered the work of demonizing it. It has been useful to people of many cultures in many places across the world but all of a sudden it’s deemed bad enough to lock people up in prison for using and selling it.

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    • Nixon was NOT the first. The “Marijauna Tax Stamp Act” was passed shortly after Prohibition ended, and was blatantly racist against (mostly) Mexicans, and Blacks, who were seen by the white power structure as being heavy users of cannabis. (Many of them were, but so were many white folks, too!) The timber industry also worked against hemp production, seeing it as a competing crop. Back then – 1930’s, – “hemp” for fiber, oil, seeds, etc., was almost the same as so-called “medical cannabis”. And yes, cannabis WAS in the U.S. Pharacopeia. So really, it’s MORE accurate to speak of RE-legalizing cannabis. I can recommend the book, “Chasing the Scream”, for a good, brief overview. I bet we’d agree that the so-called “War On(some)Drugs(sometimes)”, has done, and continues to do, far more harm than good. The local jail is at capacity with real criminals, and opioid users/addicts. It’s VERY difficult to get thrown in jail just for *weed*…. But your point is well-taken

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