An evidence-based look at cannabis as medicine, its changing legal status in the United States, and the scientific developments shaping its future.
Cannabis has one of the longest histories of human use as a medicinal plant. For thousands of years, cultures across Asia, Africa, the Middle East, and Europe have incorporated cannabis preparations into traditional healing practices. Yet its journey from ancient herbal remedy to controversial controlled substance—and now to an increasingly recognized subject of medical research—has been anything but straightforward.
Understanding this history requires separating documented historical evidence from popular myths, distinguishing industrial hemp from medicinal cannabis, and recognizing the difference between traditional medical use and modern scientific proof.
Ancient Cannabis: The Origins of Medicinal Use
Cannabis has been cultivated for thousands of years, serving as a source of fiber, food, religious ritual, and medicine. China and India are particularly important to its early medicinal history.
One frequently repeated historical account credits the legendary Chinese emperor Shénnóng, also known as Shen Nung, with identifying cannabis's medicinal properties around 2737 B.C. Traditional accounts associate cannabis with treatments for gout, rheumatism, malaria, and memory problems.
However, this date requires an important qualification. Shen Nung is a legendary figure rather than a historically verified emperor, and the medical text traditionally attributed to him was compiled centuries later. The Shénnóng Běn Cǎo Jīng reflects early Chinese herbal knowledge, but it cannot reliably establish that cannabis was prescribed in 2737 B.C.
Cannabis also appeared in traditional Indian medicine and religious practices. Some Hindu traditions associated the plant with spiritual experiences and relief from distress. Over subsequent centuries, medicinal preparations containing cannabis became part of healing traditions in different regions.
These historical accounts demonstrate longstanding human interest in cannabis as a therapeutic plant. They do not, however, establish that every condition historically treated with cannabis responds effectively to it by modern clinical standards.
Cannabis Arrives in the Americas
Cannabis's history in the Americas is closely connected to European colonization and the global hemp trade.
An often-repeated claim states that Christopher Columbus introduced cannabis to the New World in 1492 as hemp rope. Although hemp was important to European maritime industries, the specific claim about Columbus bringing cannabis on his voyage is not sufficiently established to present as fact.
A better-documented milestone occurred in 1619. Virginia's colonial assembly encouraged settlers to cultivate hemp, alongside other agricultural crops. Hemp was valuable because its strong fibers could be used to manufacture rope, sails, and textiles.
George Washington also cultivated hemp at Mount Vernon. However, historical records indicate that his interest was primarily agricultural and industrial. Hemp supplied fiber for rope, canvas, thread, and fishing equipment. Claims that Washington grew cannabis specifically for medicinal or recreational purposes are unsupported.
This distinction matters: industrial hemp and medicinal cannabis belong to the same plant species, but their cultivation purposes and chemical characteristics can differ substantially.
Cannabis Enters Western Medicine
During the 19th century, cannabis gained recognition among Western physicians.
Irish physician William Brooke O'Shaughnessy helped introduce Indian hemp to Western medical practice following his observations in India. In 1840, he published research describing its potential applications, including treatment for muscle spasms, convulsions, and other conditions.
Cannabis subsequently became available in medicinal preparations, including extracts and tinctures. By 1851, cannabis appeared in the United States Pharmacopeia, an authoritative reference for medicinal substances.
American physicians prescribed cannabis preparations for various complaints, including pain, insomnia, and neurological conditions. However, inconsistent preparations and difficulties controlling dosage limited their reliability.
The Beginning of Cannabis Prohibition
The early 20th century brought significant changes in American attitudes toward drugs and medicines.
The Pure Food and Drug Act of 1906 introduced federal regulation of food and medicine labeling, addressing problems involving undisclosed ingredients in commercial products. Contrary to some historical accounts, this legislation did not create the modern Food and Drug Administration under that name, nor did it directly prohibit cannabis.
Cannabis prohibition developed through subsequent legislation and changing political attitudes. The Marihuana Tax Act of 1937 imposed restrictive taxes and registration requirements that effectively obstructed much legitimate cannabis distribution.
Although medical cannabis was not immediately prohibited in every practical sense, the legislation made its use increasingly difficult. In 1942, cannabis was removed from the United States Pharmacopeia, further weakening its position in conventional American medicine.
The Controlled Substances Act of 1970 subsequently classified marijuana as a Schedule I substance, placing it in the category reserved for drugs considered to have a high potential for abuse and no currently accepted medical use under federal law.
This classification created substantial obstacles for researchers seeking to investigate cannabis's therapeutic potential.
Medical Cannabis and the Federal Government: The Robert Randall Case
Despite increasing restrictions, some patients continued to argue that cannabis was essential to their medical treatment.
One landmark case involved Robert Randall, a glaucoma patient who used cannabis to help manage his condition. In 1976, Randall successfully challenged federal authorities after facing prosecution for his cannabis use. His case ultimately led to his enrollment in a federal Investigational New Drug program in 1978.
Under the Compassionate Investigational New Drug (IND) program, the federal government supplied cannabis cigarettes to a small number of qualifying patients. Cannabis was cultivated at the University of Mississippi and distributed through the federal program.
In 1992, the George H. W. Bush administration stopped accepting new applicants, although existing participants were generally allowed to continue receiving their supplies.
The program became an important historical contradiction: the federal government maintained that cannabis had no accepted medical use while supplying it to certain patients for medical purposes.
The Modern Medical Cannabis Movement
During the 1990s, renewed interest in medical cannabis emerged, particularly among AIDS patients experiencing severe weight loss, nausea, and other symptoms.
California became the first U.S. state to legalize medical marijuana through Proposition 215 in 1996. Other states gradually followed, creating a growing divide between state medical cannabis programs and federal prohibition.
Research also began expanding. University of California, San Francisco, physician Donald Abrams became involved in clinical research examining smoked cannabis, including its effects in patients with HIV. These developments helped encourage further scientific investigation.
In October 2009, the Department of Justice issued guidance directing federal prosecutors to prioritize significant criminal activity rather than individuals complying with state medical marijuana laws. This represented a meaningful change in federal enforcement policy, although it did not legalize medical cannabis federally.
Other important developments followed:
2014: Congress enacted the Rohrabacher–Farr amendment, restricting the Justice Department's use of appropriated funds to interfere with state medical cannabis programs.
2018: The Agriculture Improvement Act, commonly called the Farm Bill, removed qualifying hemp from the federal Controlled Substances Act definition of marijuana. Hemp was defined by a delta-9 THC concentration of no more than 0.3% on a dry-weight basis. This did not automatically make every CBD product legal under every federal law or FDA regulation.
2022: President Joe Biden signed the Medical Marijuana and Cannabidiol Research Expansion Act into law. It established procedures intended to facilitate cannabis research and the development of potential FDA-approved medicines.
2026: A Major Change in Federal Medical Cannabis Policy
One of the most significant recent developments occurred in April 2026.
Following President Donald Trump's December 2025 executive order directing the government to expedite medical cannabis rescheduling, the Department of Justice issued a final order moving FDA-approved marijuana-containing products and qualifying state-licensed medical cannabis products into Schedule III of the Controlled Substances Act.
The order took effect on April 22, 2026, with its publication in the Federal Register on April 28.
Schedule III substances are considered to have accepted medical use and a lower potential for abuse than Schedule I substances. This represents a substantial change in the federal regulatory treatment of qualifying medical cannabis products.
However, an important distinction remains: this was not blanket federal legalization or the rescheduling of all marijuana.
State-licensed medical cannabis and FDA-approved marijuana products covered by the order received Schedule III treatment.
Recreational marijuana and cannabis outside the qualifying medical framework remained Schedule I.
The broader federal rescheduling process remained subject to further administrative proceedings.
The change also has potential tax implications. Businesses covered by the qualifying Schedule III framework are no longer subject to the Section 280E restriction in the same way as Schedule I businesses. Nevertheless, implementation and tax guidance require careful attention.
The Future of Medical Cannabis
The history of medical cannabis illustrates how scientific understanding, public opinion, and government policy can evolve over time.
Today, researchers continue investigating cannabinoids such as THC and CBD for their potential therapeutic applications. Evidence supports certain medical uses, including specific forms of chronic pain management, chemotherapy-related nausea, and particular seizure disorders. However, evidence varies considerably depending on the condition, cannabinoid, formulation, and dosage.
The distinction between promising research and established clinical effectiveness remains essential. Cannabis should not be considered a universal treatment, and historical use alone is not proof of medical benefit.
From ancient herbal traditions to modern clinical trials and federal regulatory reform, cannabis has experienced a remarkable transformation. Its future as a medicine will depend not simply on changing legislation, but on rigorous scientific research, appropriate clinical standards, patient safety, and reliable access to evidence-based treatments.