Marijuana in rolling paper

Does Weed Kill Brain Cells?

Cannabis users have long realized the many benefits of marijuana consumption. From treating anxiety disorders to seizures and chronic pain, there is no doubt cannabis has a wide array of medicinal uses 1, 2, 3 Blessing, E. M., Steenkamp, M. M., Manzanares, J., & Marmar, C. R. (2015). Cannabidiol as a Potential Treatment for Anxiety Disorders. Neurotherapeutics : the journal of the American Society for Experimental NeuroTherapeutics, 12(4), 825–836. https://doi.org/10.1007/s13311-015-0387-1 . But as a drug that interacts with the user’s brain chemistry, it’s fair for some to wonder, “does weed kill brain cells?”

How Does Weed Affect the Brain?

The effects of cannabis are achieved specifically because of how the various cannabinoids interact with the body’s endocannabinoid system (ECS). A complex system of neurotransmitters and cannabinoid receptors, the ECS operates throughout the human body, occupying the connective tissues, glands, organs, and yes, the brain 4 Alger B. E. (2013). Getting high on the endocannabinoid system. Cerebrum: the Dana forum on brain science, 2013, 14. .

The cannabis plant contains over 60 cannabinoids, with THC and CBD being among the most studied and discussed 5 Atakan Z. (2012). Cannabis, a complex plant: different compounds and different effects on individuals. Therapeutic advances in psychopharmacology, 2(6), 241–254. https://doi.org/10.1177/2045125312457586 . When cannabis is consumed, these cannabinoids bind to and activate the receptors in the ECS, disrupting the various mental and physical functions that are controlled by the ECS 6 Marijuana Research Report. (2020). National Instituted on Drug Abuse. https://www.drugabuse.gov/publications/research-reports/marijuana/how-does-marijuana-produce-its-effects .

It is this interaction with the ECS that results in both the psychoactive experience enjoyed by THC users, as well as the various positive impacts on many conditions like anxiety experienced by CBD users 1 Blessing, E. M., Steenkamp, M. M., Manzanares, J., & Marmar, C. R. (2015). Cannabidiol as a Potential Treatment for Anxiety Disorders. Neurotherapeutics : the journal of the American Society for Experimental NeuroTherapeutics, 12(4), 825–836. https://doi.org/10.1007/s13311-015-0387-1 .

This is important to understand before diving into the potential negative impacts of cannabis on the brain. Just because a drug (medicinal or recreational) interacts with the brain does not automatically mean it’s dangerous. All drugs that are meant to impact the brain chemistry interact in similar ways – often, to produce positive results.

Does Weed Kill Brain Cells?

The question of “does weed kill brain cells?” then becomes, “are marijuana’s effects on the brain short-term or can long-lasting damage occur?”

The long-term impacts on the brain of other frequently used drugs tend to be pretty well known. Chronic alcohol use, for instance, has been shown to result in permanent central nervous system damage and brain tissue damage 7 Sullivan, E. V., Harris, R. A., & Pfefferbaum, A. (2010). Alcohol’s effects on brain and behavior. Alcohol research & health : the journal of the National Institute on Alcohol Abuse and Alcoholism, 33(1-2), 127–143. .

However, research studies around the effects of marijuana use on the adult brain have produced conflicting results. While some studies have found cannabis to produce benign effects on the brain structure, others have suggested chronic marijuana use (consuming three times a day on average) can contribute to IQ deficits and gray matter loss 8, 9 DeLisi L. E. (2008). The effect of cannabis on the brain: can it cause brain anomalies that lead to increased risk for schizophrenia?. Current opinion in psychiatry, 21(2), 140–150. https://doi.org/10.1097/YCO.0b013e3282f51266 .

There continues to be a debate surrounding the potential long-term impacts of cannabis use on the brains of moderate adult users, with family studies finding no difference in amygdala volume among marijuana users 10 Pagliaccio D, Barch DM, Bogdan R, et al. (2015). Shared Predisposition in the Association Between Cannabis Use and Subcortical Brain Structure. JAMA Psychiatry. 2015;72(10):994-1001. doi:10.1001/jamapsychiatry.2015.1054 .

As a result, we don’t yet know the answer to “does weed kill brain cells?” in adult users. The research into the potential risks for developing brains, on the other hand, warrants further discussion.

Risks to Adolescent Users

Teenagers may also wonder, “does smoking weed kill brain cells?” At least, based on the research that currently exists, the answer is more likely a yes.

Several studies have found that while cannabis use can cause long-term cognitive impairments, the degree and duration of these impairments is largely connected to the age at which a person began using marijuana, with younger users experiencing more adverse effects 11 Volkow ND, Swanson JM, Evins AE, et al. (2016). Effects of Cannabis Use on Human Behavior, Including Cognition, Motivation, and Psychosis: A Review. JAMA Psychiatry. 2016;73(3):292-297. doi:10.1001/jamapsychiatry.2015.3278 . In other words, adolescent users may have more to lose when it comes to cannabis consumption.

Still, our current research isn’t definitive. While studies seem to suggest a greater risk of damage to developing brains as opposed to adult brains, reviews of existing research have concluded that there is a need for more longitudinal studies. This further research is needed to identify whether or not structural brain differences are a result of early marijuana use or of pre-existing differences that then lead to increased risks of substance use 12 Jacobus, J., & Tapert, S. F. (2014). Effects of cannabis on the adolescent brain. Current pharmaceutical design, 20(13), 2186–2193. https://doi.org/10.2174/13816128113199990426 .

Given the body of research we currently have, it is safe to say adolescents should exercise more caution when considering marijuana use than their adult counterparts 13 Shen, Helen. (2020). News Features: Cannabis and the Adolescent Brain. Proceedings of the National Academy of Sciences of the United States of America. https://www.pnas.org/content/117/1/7 .

Risks of Using Cannabis During Pregnancy

It’s one thing to ask, “does smoking weed kill your brain cells?” But it’s another thing entirely to question whether or not your marijuana use could kill the brain cells of someone else. This is a question that pregnant individuals must ask themselves when considering the potential impact of maternal use of cannabis on a fetus’s developing brain.

While we do have research that suggests marijuana use during pregnancy can contribute to potential health issues such as low birth weight (as well as research that contradicts those claims), there is thus far no research indicating an impact on neonatal brain development 14 Gunn JK, Rosales CB, Center KE, et al. (2016). Prenatal exposure to cannabis and maternal and child health outcomes: a systematic review and meta-analysis. BMJ Open. 2016;6(4):e009986. Published 2016 Apr 5. doi:10.1136/bmjopen-2015-009986 . That does not mean an impact doesn’t exist, however.

Human studies on the impacts of maternal behavior on a developing fetus can be hard to come by, but animal studies have found that perinatal exposure to cannabis does contribute to significant learning and memory struggles later in life 15 Campolongo, P., Trezza, V., Cassano, T., Gaetani, S., Morgese, M. G., Ubaldi, M., Soverchia, L., Antonelli, T., Ferraro, L., Massi, M., Ciccocioppo, R., & Cuomo, V. (2007). Perinatal exposure to delta-9-tetrahydrocannabinol causes enduring cognitive deficits associated with alteration of cortical gene expression and neurotransmission in rats. Addiction biology, 12(3-4), 485–495. https://doi.org/10.1111/j.1369-1600.2007.00074.x .

This research, combined with what we know about the potential impacts of marijuana use on developing adolescent brains, suggests individuals should exercise extreme caution and talk to their doctors before engaging in cannabis use while pregnant.

So, Are There Long-Term Effects?

While various studies are looking into the long-term effects of marijuana on the brain, the results thus far have varied. This means we can’t definitively answer the question of “does weed kill brain cells?” 16 Filbey, F. M., Aslan, S., Calhoun, V. D., Spence, J. S., Damaraju, E., Caprihan, A., & Segall, J. (2014). Long-term effects of marijuana use on the brain. Proceedings of the National Academy of Sciences of the United States of America, 111(47), 16913–16918. https://doi.org/10.1073/pnas.1415297111 .

We know that if marijuana does kill brain cells, the risks are greater for chronic adult users and those with developing brains. As a result, adolescents should avoid marijuana use unless instructed by a doctor to consume marijuana for medicinal purposes. And in regards to chronic adult marijuana users, they should discuss their usage with a doctor to determine individual risks and explore the potential benefits of reducing the amount of marijuana they consume.

Sources
  1. Blessing, E. M., Steenkamp, M. M., Manzanares, J., & Marmar, C. R. (2015). Cannabidiol as a Potential Treatment for Anxiety Disorders. Neurotherapeutics : the journal of the American Society for Experimental NeuroTherapeutics, 12(4), 825–836. https://doi.org/10.1007/s13311-015-0387-1
  2. Piper, B. J., Beals, M. L., Abess, A. T., Nichols, S. D., Martin, M. W., Cobb, C. M., & DeKeuster, R. M. (2017). Chronic pain patients' perspectives of medical cannabis. Pain, 158(7), 1373–1379. https://doi.org/10.1097/j.pain.0000000000000899
  3. Perucca E. (2017). Cannabinoids in the Treatment of Epilepsy: Hard Evidence at Last?. Journal of epilepsy research, 7(2), 61–76. https://doi.org/10.14581/jer.17012
  4. Alger B. E. (2013). Getting high on the endocannabinoid system. Cerebrum: the Dana forum on brain science, 2013, 14.
  5. Atakan Z. (2012). Cannabis, a complex plant: different compounds and different effects on individuals. Therapeutic advances in psychopharmacology, 2(6), 241–254. https://doi.org/10.1177/2045125312457586
  6. Marijuana Research Report. (2020). National Instituted on Drug Abuse. https://www.drugabuse.gov/publications/research-reports/marijuana/how-does-marijuana-produce-its-effects
  7. Sullivan, E. V., Harris, R. A., & Pfefferbaum, A. (2010). Alcohol's effects on brain and behavior. Alcohol research & health : the journal of the National Institute on Alcohol Abuse and Alcoholism, 33(1-2), 127–143.
  8. DeLisi L. E. (2008). The effect of cannabis on the brain: can it cause brain anomalies that lead to increased risk for schizophrenia?. Current opinion in psychiatry, 21(2), 140–150. https://doi.org/10.1097/YCO.0b013e3282f51266
  9. Filbey, F. M., Aslan, S., Calhoun, V. D., Spence, J. S., Damaraju, E., Caprihan, A., & Segall, J. (2014). Long-term effects of marijuana use on the brain. Proceedings of the National Academy of Sciences of the United States of America, 111(47), 16913–16918. https://doi.org/10.1073/pnas.1415297111
  10. Pagliaccio D, Barch DM, Bogdan R, et al. (2015). Shared Predisposition in the Association Between Cannabis Use and Subcortical Brain Structure. JAMA Psychiatry. 2015;72(10):994-1001. doi:10.1001/jamapsychiatry.2015.1054
  11. Volkow ND, Swanson JM, Evins AE, et al. (2016). Effects of Cannabis Use on Human Behavior, Including Cognition, Motivation, and Psychosis: A Review. JAMA Psychiatry. 2016;73(3):292-297. doi:10.1001/jamapsychiatry.2015.3278
  12. Jacobus, J., & Tapert, S. F. (2014). Effects of cannabis on the adolescent brain. Current pharmaceutical design, 20(13), 2186–2193. https://doi.org/10.2174/13816128113199990426
  13. Shen, Helen. (2020). News Features: Cannabis and the Adolescent Brain. Proceedings of the National Academy of Sciences of the United States of America. https://www.pnas.org/content/117/1/7
  14. Gunn JK, Rosales CB, Center KE, et al. (2016). Prenatal exposure to cannabis and maternal and child health outcomes: a systematic review and meta-analysis. BMJ Open. 2016;6(4):e009986. Published 2016 Apr 5. doi:10.1136/bmjopen-2015-009986
  15. Campolongo, P., Trezza, V., Cassano, T., Gaetani, S., Morgese, M. G., Ubaldi, M., Soverchia, L., Antonelli, T., Ferraro, L., Massi, M., Ciccocioppo, R., & Cuomo, V. (2007). Perinatal exposure to delta-9-tetrahydrocannabinol causes enduring cognitive deficits associated with alteration of cortical gene expression and neurotransmission in rats. Addiction biology, 12(3-4), 485–495. https://doi.org/10.1111/j.1369-1600.2007.00074.x
  16. Filbey, F. M., Aslan, S., Calhoun, V. D., Spence, J. S., Damaraju, E., Caprihan, A., & Segall, J. (2014). Long-term effects of marijuana use on the brain. Proceedings of the National Academy of Sciences of the United States of America, 111(47), 16913–16918. https://doi.org/10.1073/pnas.1415297111

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