A Canadian study suggests strong marijuana can cause changes in the developing brain similar to those in the brains of schizophrenics.

A Canadian study suggests strong marijuana can cause changes in the developing brain similar to those in the brains of schizophrenics.
Photo Credit: Western University/Schulich Medicine & Dentistry

Marijuana alters adolescent brain chemistry: study


Adolescent rats exposed to the active ingredient in marijuana, THC, experience molecular changes in the brain that resemble those in schizophrenia, found a recent study from Western University. These changes did not occur in adult rats exposed in the same way. Marijuana is said to be the most commonly used illegal drug in Canada. 44 per cent of Canadians say they have used it at least once.

“Not only did we see molecular changes in the brain that were very consistent with what we see in the brain of a human that has schizophrenia, we saw this very profound disregulation of the dopamine system which is also a very important pathology that’s associated with schizophrenia,” said Prof. Steven Laviolette who worked on the study.

Associate Prof. Steven Laviolette and lead author Justine Renard look at evidence from their study of THC’s molecular effect on the brain.
Associate Prof. Steven Laviolette and lead author Justine Renard look at evidence from their study of THC’s molecular effect on the brain. © Western University/Schulich Medicine & Dentistry

Other studies suggest psychiatric effects too

These results are consistent with other scientific evidence that has come out recently showing that if teenagers are exposed to high levels of marijuana during brain development they are at increased risk of developing psychiatric problems in later adulthood such as schizophrenia. Until now, it was not clear what the underlying mechanisms are.

This study could in future help predict who is most likely to suffer these kinds of effects.

A need to be cautious, says researcher

The newly-elected prime minister of Canada has vowed to legalize marijuana and Laviolette thinks this study is highly relevant. “What these findings suggest is that we really do need to be cautious about restricting access to, especially strains of marijuana that have high levels of THC, to young adolescents—teenagers that are going through a period of brain development.”

“In many ways, I think it speaks in favour of a legalization approach because it allows the government to more closely regulate the amounts of THC that are in strains of marijuana and also provide access points that are regulated and controlled, as opposed to the black market which really has no regulation at all,” concludes Laviolette.

The study was published in the January issue of the journal Cerebral Cortex.

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4 comments on “Marijuana alters adolescent brain chemistry: study
  1. Out of balance brain chemistry can cause depression, anxiety, eating disorders, sugar and carbohydrate cravings, weight gain, addictive personality, reckless/risky behaviour and of course bipolar syndrome.

  2. Avatar Cheech says:

    more bull excrement from pseudo scientists and their fawning presstitutes – an embarrassment to even publish this discredited research.

  3. Avatar Malcolm Kyle says:

    Health concerns regarding marijuana tend to come from a self-fueling group of discredited scientists funded by the pharmaceutical, prison, tobacco, and alcohol industries. They push non-peer-reviewed papers, fraught with conjecture and confounding variables, while relying upon reports issued by others in their own group to further support their own grossly misleading research and clearly biased agendas.

    The Duke University (New Zealand) study, the one which claimed that smoking marijuana in your teens leads to a long-term drop in IQ, has since been utterly rebuked by a new paper published by the Proceedings of the National Academy of Sciences. They examined the research and found its methodology to be flawed.

    “…existing research suggests an alternative confounding model based on time-varying effects of socioeconomic status on IQ. A simulation of the confounding model reproduces the reported associations from the [August 2012 study], suggesting that the causal effects estimated in Meier et al. are likely to be overestimates, and that the true effect could be zero”.
    —Ole Rogeberg.

    Source: http://www.salon.com/2013/01/15/actually_pot_may_not_lower_iq_after_all/

    “The conclusions were modest in the paper. we never say marijuana causes these changes. The media may have given that impression in headlines, but the study doesn’t show causation. I think I saw one headline that was ‘Marijuana reshapes the brain’ and I groaned –that’s not what we did,”

    — Dr. Jodi Gilman, 31, author of the Harvard Medical School/Massachusetts General Hospital study on marijuana’s effects, in an interview with PolicyMic.  

  4. Avatar Malcolm Kyle says:

    Study: Cannabis Use Not Predictive Of Lower IQ, Poorer Educational Performance

    “… to test the relationships between cumulative cannabis use and IQ at the age of 15 and educational performance at the age of 16. After full adjustment, those who had used cannabis ⩾50 times did not differ from never-users on either IQ or educational performance. Adjusting for group differences in cigarette smoking dramatically attenuated the associations between cannabis use and both outcomes, and further analyses demonstrated robust associations between cigarette use and educational outcomes, even with cannabis users excluded. These findings suggest that adolescent cannabis use is not associated with IQ or educational performance once adjustment is made for potential confounds, in particular adolescent cigarette use.”

    Source: C Mokrysz, et al. Clinical Psychopharmacology Unit, University College London. Published January 6, 2016 in Journal of Psychopharmacology.


    Daily Marijuana Use Is Not Associated with Brain Morphometric Measures in Adolescents or Adults

    “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. 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.”

    The Journal of Neuroscience, 28 January 2015, 35(4): 1505-1512; doi: 10.1523/JNEUROSCI.2946-14.2015