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Throughout its long history with humans, the cannabis plant has been both praised and criminalized. The latter has stunted research possibilities, most notably in the United States since its initial categorization in the 70s as a Schedule 1 drug.
Still, curious and sometimes outright rebellious researchers have persisted and have uncovered what ancient societies inherently understood thousands of years ago: This botanical has therapeutic properties.
We now have more than 15,000 modern peer-reviewed scientific articles on the chemistry and pharmacology of cannabis and cannabinoids, as well as more than 2,000 articles on the body's natural cannabinoids and associated internal receptors.
Every study has its own significance in furthering our understanding of cannabis, but several in particular are cited time and time again. These stand as the groundbreaking studies that altered perceptions and opened new paths to explore the true potential of this plant in human society.
These are the most groundbreaking cannabis studies across time.
As the British colonized India, government officials in parliament grew concerned about the locals use of hemp drugs in Bengal, India. This lead to questions about the safety of the plant on all aspects of health from the physical to the mental to the social.
In a search for answers, the House of Commons of the United Kingdom commissioned British and Indian researchers to study its sociological effects first in Bengal and then extending to all of India.
This was the first comprehensive study of its kind. The result was over 3,000 pages and contained insights from over 1200 “doctors, coolies, yogis, fakirs, heads of lunatic asylums, bhang peasants, tax gatherers, smugglers, army officers, hemp dealers, ganja palace operators, and the clergy.”
Upon publication in 1894, the commission concluded it would be unjust to prohibit hemp use because consumption is essentially harmless and potentially even beneficial.
As we know though, despite the thoroughness of this commission, it didn’t prevent the misconceptions of Reefer Madness in the years to come.
This report came as an official response to Reefer Madness rumours flooding airwaves.
Reefer Madness refers to the fear mongering campaigns presented by head of the Federal Bureau of Narcotics, Harry J. Anslinger. These campaigns equated consuming cannabis with the consequence of madness.
Fiorello LaGuardia, New York City Mayor, commissioned this report on the advisement of The New York Academy of Medicine.
In the official release, LaGuardia calms concerned citizens with science: “I am glad that the sociological, psychological, and medical ills commonly attributed to marihuana have been found to be exaggerated insofar as the City of New York is concerned.”
He continued, “I hasten to point out, however, that the findings are to be interpreted only as a reassuring report of progress and not as encouragement to indulgence, for I shall continue to enforce the laws prohibiting the use of marihuana until and if complete findings may justify an amendment to existing laws.”
Even though the report wasn’t enough to change existing laws, it was enough to dispel myths beyond those strictly referring to Reefer Madness. In its nearly 80 pages, mental health professionals, chemists, sociologists and more argued against other misconceptions like that cannabis leads to opiate abuse or antisocial behaviour.
They also acknowledged the potential therapeutic effects of the plant and suggested further research on the subject. LaGuardia agreed, stating, “The scientific part of the research will be continued in the hope that the drug may prove to possess therapeutic value for the control of drug addiction.”
The Discovery of THC (1964)
The discovery of Tetrahydrocannabinol (THC) is quite arguably the most significant finding in cannabis studies as it opened the door to a plethora of new research paths that has helped society better understand the chemical composition and true complexity of this plant.
Attributed to an Israeli organic chemist named Raphael Mechoulam and his team of researchers, THC was found from a place of curiosity of Mechoulam’s part.
In an interview with National Geographic, Mechoulam explains how he found it odd that while “morphine had been teased from opium in 1805 and cocaine from coca leaves in 1855, scientists had no idea what the principal psychoactive ingredient was in marijuana.”
Working with police-confiscated Lebanese hashish, Mechoulam experimented with isolating substances within the plant and monitoring how Rhesus monkeys reacted to exposure.
The only substance that had any effect was what we now know as THC. It calmed and almost sedated the monkeys, leading to more tests and the eventual understanding of THC as the psychoactive compound in cannabis.
This same team is also responsible for the discovery of the non-psychoactive cannabinoid Cannabidiol, or CBD, in the sixties.
National Commission on Marihuana and Drug Abuse (1972)
Also known as The Shafer Commission Report after its lead, Raymond P. Shafer, former Republican Governor of Pennsylvania, the historical significance of this publication cannot be underestimated.
In 1970, cannabis was classified as a Schedule 1 drug in the United States, meaning it was deemed unsafe and without any medicinal properties. In 1971, President Nixon declared the war on drugs, setting into motion a social and political divide that continues even today.
Nixon strategically commissioned this report to support his anti-cannabis stance and reinforce policies, but it did just the opposite. Boldly standing up to congress, the report recommended a new approach: decriminalization.
The commission states, “The actual and potential harm of use of the drug is not great enough to justify intrusion by the criminal law into private behavior, a step which our society takes only with the greatest reluctance … Therefore, the Commission recommends ... [that] possession of marijuana for personal use no longer be an offense, [and that] casual distribution of small amounts of marihuana for no remuneration, or insignificant remuneration, no longer be an offense.”
The report directly criticized existing policies, stating that “Unless present policy is redirected, we will perpetuate the same problems, tolerate the same social costs, and find ourselves as we do now, no further along the road to a more rational legal and social approach than we were in 1914.”
Of course, the recommendations from this congress-appointed panel of researchers were not received well. Nixon shelved the report and continued to ramp up the war on drugs, leading to more cannabis-related arrests and imprisonments.
This report remains as the last review on cannabis policy from the federal government in the United States.
Animal Studies Show THC Slows Tumour Growth (1975)
Published in the Journal of the National Cancer Institute, this groundbreaking study shows THC and another, much lesser known cannabinoid called cannabinol (CBN), have properties that slow lung tumour growth. At the time, CBD was found to have no significant effect.
The experiments found that “animals treated for 10 consecutive days with Δ9-THC, beginning the day after tumor implantation, demonstrated a dose-dependent action of retarded tumor growth. Mice treated for 20 consecutive days with Δ8-THC and CBN had reduced primary tumor size.”
Since then, cannabis’ effects on tumours have been studied in different types of cancers. In 2016, a research review published by Current Oncology compiled evidence for cannabinoids as anti-cancer agents, identifying their potential to kill cancer cells, but not necessarily “cure” cancer.
Most recently, the Journal of Physiology and Biochemistry published a peer-reviewed study showing CBD’s therapeutic potential in treating endometrial cancer due to its ability to kill cancer cells.
While research wages on, we can point to this original study as a starting point for understanding the often widely-misunderstood connection between cannabis and cancer.
Anecdotal evidence lead researchers to question the potential of cannabis in treating chemotherapy-induced nausea and vomiting.
Working with chemotherapy patients, the placebo-controlled "double-blind" study found significant positive effects for reducing adverse reactions from cancer-related drug therapies: “Oral tetrahydrocannabinol has antiemetic properties and is significantly better than a placebo in reducing vomiting caused by chemotherapeutic agents.”
Side effects included feeling “high” and appetite simulation.
This research further legitimized cannabis’ role in cancer treatment and paved the way for medical access to the symptom-relieving botanical.
Today, it’s widely accepted that cannabis can reduce and relieve chronic pain in patients across diagnoses from cancer to AIDs to fibromyalgia.
However, the road to understanding the complexity of cannabis as a pain-reliever has been bumpy. You can find a lot contradictory evidence in early years, before researchers found that different doses of THC have different effects of pain.
This study, titled The analgesic properties of delta-9-tetrahydrocannabinol and codeine, is the first controlled study of its kind to note this difference in dosing. It paved the way for a deeper understanding of THC’s role in pain management.
Researchers found that while low doses (10mg) of THC had a mild analgesic effect, higher doses (20mg) were associated with adverse side effects like dizziness and blurred vision to the point where it proved counterproductive for patients seeking relief.
CBD’s role in reducing seizures in patients with epilepsy did not begin with the commonly cited story of a young girl with Dravet Syndrome named Charlotte who saw life-changing improvements after being administered the high-CBD strain we now call Charlotte’s Web.
Although limited by a small sample size, this controlled study spearheaded society’s acceptance of cannabis use for modulating seizures in patients with epilepsy. Researchers found 4 of 8 human subjects were almost free of convulsive episodes during the trial, with another 3 subjects finding partial improvement in their condition. Perhaps more significant for the future of cannabis research, CBD provided these results without adverse reactions commonly associated with the cannabinoid THC.
THC is a More Effective for Treatment Alzheimer’s Than Current Medication Options (2006)
While this isn’t the first study conducted on the connection between cannabis and Alzheimer's disease, it wins a spot on this list because of its finding that THC is more effective at slowing the disease’s progression than marketed pharmaceuticals like donepezil and tacrine.
With Alzheimer’s rates expected to triple in the next 50 years, this study provides hope that we can combat its progression with cannabis. It also spurred more research in this area, further strengthening the initial finding.
Cannabis Doesn’t Cause Lung Cancer (2006)
While most of the groundbreaking work on this list has featured what cannabis can do for humans, we also need to pay attention to research on potential long-term side effects of consumption.
In this landmark study, researchers led by Donald Tashkin of the University of California, a pulmonologist who has been studying cannabis for 30 years, set out to see the connection between cannabis consumption and lung cancer.
Tashkin reports to the Washington Post that his team “hypothesized that there would be a positive association between marijuana use and lung cancer, and that the association would be more positive with heavier use.”
Instead, he continued, "What we found instead was no association at all, and even a suggestion of some protective effect."
This was the largest study of its kind and effectively negates old assumptions that cannabis smoking causes lung cancer.
Widely cited and highly revered, Ethan B Russo’s extensive review significantly enhanced our understanding of the relationship between chemical compounds present in the plant. Most significantly, it highlighted the concept of cannabis synergy and the entourage effect, that is, that certain cannabinoids (like THC and CBD) can be paired to produce more desirable effects than possible when dosing isolates. In such cases, CBD mitigates the adverse reactions many experience from THC and improves overall therapeutic profiles of the plant.
While it draws from collective works, this review brought forth a strong understanding of why whole plant medicine is more effective. The impact on medical patients seeking appropriate dosing and strains is invaluable.
Cannabis Reduces Opioid Overdoses (2014)
Previously stigmatized as a “gateway drug,” this study argues cannabis can actually be a crucial component in preventing drug overdoses from opioids. It set the stage for further research confirming cannabis’ potential role in treating drug addictions.
Building from Dr. Donald Abrams’ work in 2011 that found cannabis can make more opioids more effective, thus effectively reducing the need for higher, more dangerous doses, this work highlights the connection between cannabis legalization and lower rates of opioid overdoses: “States with medical cannabis laws had a 24.8% lower mean annual opioid overdose mortality rate compared with states without medical cannabis laws.”
This research spurred a series of studies that show cannabis has potential in harm reduction programs. Most notably, two new studies published in 2018 argue that access to cannabis actually reduces opioid prescriptions. In the current opioid crisis climate, this research has the potential to save lives.