Why Isn’t the ECS Taught in Medical School?

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A medical school professor investigates why the endocannabinoid system isn't taught in American medical schools.

As a former medical school professor who taught Gross Anatomy, I was amazed when I learned that there was an endocannabinoid system (ECS) and that it maintains homeostasis. Homeostasis is a core principle of physiology and a critically important function of the body.1 It is the mechanism that maintains balance in the barrage of internal and external environmental changes. Maintaining homeostasis is critical to human health; thus, it is paramount that doctors, who play such a crucial role in human health, are educated on the ECS in medical school.

The ECS Is Omnipresent

The ECS is often described as only being in the nervous and immune systems, where the highest density of ECS components is found. However, it is important to point out that ECS components are found in cells throughout the body and perform critical functions in all systems of the body (Figure).   

Figure. The omnipresent endocannabinoid system (ECS). Often, the ECS is described as only being in the nervous and immune systems, which is where the highest density of ECS components is found. However, it’s important to point out that ECS components are found in cells throughout the body and perform critical functions in all systems of the body.
Credit: Cannabis Education Solutions.

Collectively, the ECS molecules sustain balance in the biochemical and physiologic processes that occur in different cells in the body. The ECS is made up of 3 sets of molecules:

  1. Endocannabinoids, which include anandamide (AEA) and 2-arachidonoyl glycerol (2-AG);
  2. The enzymes which synthesize and degrade endocannabinoids; and
  3. CB1 and CB2, the receptors that bind to the endocannabinoids.2  

Plant Cannabinoids Mimic Endocannabinoids

Interestingly, the cannabinoids found in cannabis have a similar structure to the endocannabinoids in the body and exert their effects directly or indirectly via the CB1 and CB2 receptors. Both endocannabinoids and phyto- or plant-cannabinoids regulate critical functions in the human body, including processing emotions, sleep, eating, inflammation, pain, and temperature control.3

Credit: Getty Images.

According to Lowe et al., “The ECS has increasingly become a favorable target for the treatment of various diseases as many of its components are distributed widely throughout the body and take part in cell-signaling pathways involved in the pathophysiology of many types of diseases.”4

It makes sense then that cannabis is being studied for such a wide variety of conditions. Years of Schedule I status and the stigma surrounding cannabis, however, have created barriers to studying it as medicine. For this reason, I believe even though the ECS is a molecular target for the cannabinoids and terpenes found in cannabis, it has been deemed unteachable to doctors. 

Cannabis As Medicine

Humans had been using cannabis as medicine for nearly 5000 years until Harry Anslinger, head of the US Federal Bureau of Narcotics, demonized and criminalized it.5 This eventually led to the Marihuana Tax Act in 1937, which made it illegal to possess or sell, and then to the Controlled Substance Act, led by President Richard Nixon in 1971, which classified cannabis as an illegal and dangerous Schedule I substance.6 Today, cannabis in the United States remains illegal at the federal level, with a patchwork of different regulations at the state level. In April 2021, the American Medical Association (AMA), which wields immense power, published its latest stance on cannabis: “Our AMA does not support legalization of cannabis for adult use until additional scientific research has been completed to fully document the public health, medical and economic consequences of its use.”7

However, the reality is that there is already an adequate amount of peer-reviewed scientific research on cannabis use and the ECS as a therapeutic target. If we look at the published research on how dysfunction in the ECS might be related to disease, we see a wealth of research and immense potential for cannabinoid-based therapies to target the ECS. Table 1 lists the number of scholarly articles published in PubMed as of March 2019 vs the number published as of April 2023 using the search criteria of “ECS” and “major cause of death,” (major cause of death, as listed in the Centers for Disease and Control and Prevention’s 2021 “FastStats: Leading Cause of Death”8.  In just over 4 years, the number of academic papers published in PubMed has more than doubled. This raises the question of why US medical schools are not putting more resources into teaching the ECS and why influential organizations like the AMA are not endorsing research that increases the understanding of ECS’ role in promoting health and preventing disease.

Table 1. Peer-Reviewed Research Mentioning the “ECS” and “Major Cause of Death”

   Publications as of March 2019:Publications as of April 2023
Major cause of death  
Cardiovascular disease99435
Respiratory disease3277
Alzheimer’s disease63226
Diabetes mellitus240339
ECS, endocannabinoid system.
Based on data from references 8.

So Why Isn’t the ECS Taught in Medical Schools?

To shed light on this question, I conducted interviews with 3 physicians and an academic administrator:

  • Sandra Swann, MD, a retired Family Practice Physician in Rockville, MD, succinctly said, “The cannabis industry has not been fully embraced. There are sociopolitical-legal-financial factors at play.”  
  • Brooke Worster MD, a Pain Management and Palliative Medicine Physician at Sidney Kimmel Medical College and Associate Professor and Program Director at Thomas Jefferson University (TJU) College of Health Professions in Philadelphia, PA, said, “It’s not just medical schools, but also pharmacy and nursing schools.” Dr. Worster, who led a team of colleagues to create 3 cannabis master’s programs at TJU’s College of Health Professions, noted that the answer is multifaceted. “There is a long-standing sociopolitical issue where generations of people have heard that cannabis is a bad gateway drug—decades of this thinking has piled up. Additionally, there is the perception of potheads, fear of losing federal funding, and the AMA, which has a lot of influence and is very conservative.” Although Dr. Worster faced many barriers while trying to obtain approval for the cannabis master’s programs at TJU, she found the biggest hurdle was negotiating with the Legal Department to ensure that students in the program could apply for financial aid. “Somehow, they felt this suggested that the institution was endorsing cannabis,” said Dr. Worster. She sees change happening, “albeit very slowly.”
  • Ruth Charbonneau, JD, RN, Associate Director of the Lambert Center for the Study of Medicinal Cannabis and Hemp at TJU College of Health Professions, said, “The role of the federal government, the Drug Enforcement Agency (DEA) and National Institute on Drug Abuse also impacts teaching information about illegal substances, which cannabis became in 1970 with the Controlled Substance Act (CSA).” Ms. Charbonneau notes that the CSA Schedule 1 status complicates research. She also shared that “there are pockets of people with interest in cannabis, but there’s limited opportunities to add cannabinoid medicine to the curriculum, which is already jam-packed with educational information.” As a lawyer and nurse who has worked in community hospitals, home care, urgent care, and government and academic medical centers in oncology and pediatrics, Ms. Charbonneau has a broad view of patient care. “The Lambert Center is among the forefront of institutions offering a variety of cannabis educational opportunities. The seminars are always packed with health care providers, perhaps because the patient population’s knowledge of cannabis medicine is increasing faster than the doctors can learn about it”.  
  • Jordan Tishler, MD, President of the Association of Cannabinoid Specialists (ACS) and Instructor of Medicine at Harvard Medical School, said: “There are some medical schools teaching it as they adopt cannabinoid medicine into their curricula, but there are far too few doing it, as academic medicine is very conservative and slow to adopt novel approaches.” Dr. Tishler noted that cannabinoid medicine has the additional complication of Schedule I status and nearly a century of stigma. “However, the Biden Administration has directed HHS [Health and Human Services] to review this Schedule I status, which is a hopeful sign. Ultimately, the decision rests with the DEA, not HHS or the FDA.” Although decision makers commonly claim that more data are needed, Dr. Tishler feels adequate data already exist. “The 2017 National Academy of Science report states that evidence that cannabinoids work for the treatment of pain was “incontrovertible” and that cannabinoids improved muscle spasms in multiple sclerosis and chemotherapy-induced nausea and vomiting.”10 Dr. Tishler has spent many years trying to get Harvard Medical School to include the ECS and the medical use of cannabinoids in its curriculum but to no avail. “Some institutions have added this information, but typically in their pharmacy schools, leaving out the group that needs it most—the physician. Most patients using cannabinoids are getting their advice from unreliable sources like friends or budtenders. As patients ask their physicians about cannabis as medicine, it will help reinforce the need for doctors to be adequately educated on the ECS,” said Dr. Tishler. “Until then, physicians must learn this information from other reputable sources like the ACS and be able to bring it up with their patients who might benefit instead of waiting.”

In conclusion, there is adequate scientific evidence that cannabis is medicine. It is not a Schedule I drug, defined as drugs with no currently accepted medical use and a high potential for abuse. In states that have legalized medical cannabis, a 25% decrease in opioid prescriptions and deaths is often seen.9.10 Obviously, the cannabis connection stigma is powerful, but it is a major loss that the ECS is not taught in most medical schools, and this paradigm must change!


  1. Michael J, McFarland J. The core principles (“big ideas”) of physiology: results of faculty surveys. Adv Physiol Educ. 2011;35(4):336-41. doi: 10.1152/advan.00004.2011. PMID: 22139767.
  2. Lu HC, Mackie K. An introduction to the endogenous cannabinoid system. Biol Psychiatry. 2016;79(7):516-25. doi: 10.1016/j.biopsych.2015.07.028
  3. Grinspoon P. Harvard Health. The endocannabinoid system: Essential and mysterious. Harvard health publishing. Accessed July 9 2023. https://The+endocannabinoid+system%3A+Essential+and+mysterious&rlz=1C1CHBF_enUS735US735&oq=The+endocannabinoid+system%3A+Essential+and+mysterious&gs_lcrp=EgZjaHJvbWUyBggAEEUYOdIBBzQyMGowajmoAgCwAgA&sourceid=chrome&ie=UTF-8
  4. Lowe H, Toyang N, Steele B, Bryant J, Ngwa W. The endocannabinoid system: a potential target for the treatment of various diseases. Int J Mol Sci. 2021;22(17):9472.
  5. Questions still surround cannabis use and public health. Accssed July 9, 2023. Questions still surround cannabis use and public health | American Medical Association (ama-assn.org)
  6. Boston Political Review. Henry J. Anslinger and the origins of the war on drugs. Acessed July 9, 2023. https://www.bostonpoliticalreview.org/post/harry-j-anslinger-and-the-origins-of-the-war-on-drugs
  7. National Academies of Sciences, Engineering, and Medicine. The health effects of cannabis and cannabinoids: the current state of evidence and recommendations for research. Washington, DC: The National Academies Press. https://doi.org/10.17226/24625.
  8. Centers for Disease Control and Prevention. 2021 FastStats: Leading Causes of Death. Accessed July 13, 2023. https://www.cdc.gov/nchs/fastats/leading-causes-of-death.htm
  9. Americans for Safe Access. Testimony for the president’s commission on combating drug addiction and the opioid crisis. Accessed July 13, 2023. https://www.safeaccessnow.org/presidentopioidcomissionstatement
  10. Americans for Safe Access. ASA files freedom of information act requests. Accessed July 13, 2023. https://www.safeaccessnow.org/foia