If you have spent any time reading about medicinal cannabis, you have probably noticed a recurring theme: researchers keep saying "more studies are needed." For a plant that millions of people use regularly, and that has been used medicinally for thousands of years, this can feel frustrating and even suspicious. Why don't we know more?
The answer is largely structural. The same government that millions of Americans now rely on to regulate legal cannabis markets spent more than 50 years making it nearly impossible to study the plant scientifically. Understanding this history is essential for anyone who wants to read cannabis research critically and make informed decisions.
The Schedule I Classification
How Cannabis Became the Most Restricted Substance
In 1970, President Richard Nixon signed the Controlled Substances Act, which created a classification system for drugs based on their potential for abuse and accepted medical use. Cannabis was placed in Schedule I — the most restrictive category possible. Schedule I is legally defined as substances with "no currently accepted medical use and a high potential for abuse."
To put this in context, cannabis shares Schedule I status with heroin and LSD. Meanwhile, cocaine is classified as Schedule II (lower restriction), fentanyl is Schedule II, and methamphetamine is Schedule II. All of those substances are considered to have accepted medical uses under federal law. Cannabis, according to the federal government, does not — despite the fact that 38+ states have legalized it for medical purposes.
Cannabis has been classified as a Schedule I substance under federal law since 1970 — the same category as heroin — defined as having "no currently accepted medical use and a high potential for abuse." This classification has made it extraordinarily difficult for researchers to study cannabis.
TryCannabis Research Report, Part Nine
This classification was not based on rigorous scientific review. Nixon's own commission — the Shafer Commission, which he appointed to study the issue — recommended in 1972 that cannabis be decriminalized. Nixon rejected the recommendation. Many historians attribute the scheduling decision to political motivations rather than scientific evidence.
How Classification Blocks Research
Schedule I classification creates a cascade of barriers that have effectively starved cannabis research for decades:
Federal Licensing Requirements
Any researcher who wants to study cannabis must obtain a special federal license from the Drug Enforcement Administration (DEA). The application process is lengthy, invasive, and bureaucratic. Researchers must demonstrate secure storage facilities, submit to inspections, and navigate a regulatory maze that does not apply to researchers studying most other substances — including opioids.
Limited Approved Sources
For decades, all cannabis used in federally approved research had to come from a single source: a farm at the University of Mississippi operated under contract with the National Institute on Drug Abuse (NIDA). Researchers and patients alike have long criticized this cannabis for being of low quality and not representative of what is actually available in state-legal markets. If a researcher wanted to study the effects of a high-THC strain sold in Colorado dispensaries, they could not legally obtain it for their study — they had to use whatever the Mississippi farm provided.
This has begun to change. In 2021, the DEA approved additional cannabis growers for research purposes, but the effects of this expansion are still catching up to decades of restriction.
Funding Bias
Federal research funding has historically been heavily biased toward studying the harms of cannabis rather than its potential benefits. NIDA's stated mission includes studying drug abuse, not drug therapeutics. Researchers who wanted to study whether cannabis could help patients had a much harder time securing federal funding than researchers studying its risks. This has created a lopsided evidence base where we know more about what cannabis can do wrong than what it might do right.
Institutional Risk Aversion
Universities, hospitals, and research institutions that receive federal funding have historically been cautious about cannabis research. The legal complexity and reputational risk of studying a Schedule I substance discouraged many researchers from entering the field, even when they were personally interested in the science.
Why Observational Studies Are Not the Same as RCTs
Understanding the difference between types of evidence is one of the most important skills you can develop as a consumer of cannabis research.
The Hierarchy of Evidence
| Evidence Type | What It Is | Strength | Limitation |
|---|---|---|---|
| Randomized Controlled Trial (RCT) | Participants are randomly assigned to receive either the treatment or a placebo. Neither the participants nor the researchers know who received what (double-blind). | Gold standard — can demonstrate causation | Expensive, time-consuming, and difficult to blind with cannabis (people notice if they get high) |
| Cohort Study | Researchers follow a group of people over time, observing outcomes without intervening. Example: the Johns Hopkins anxiety study. | Can show strong associations over time | Cannot prove causation; participants self-select |
| Cross-Sectional Survey | Researchers collect data from a group of people at a single point in time. | Quick, inexpensive, can reveal patterns | Snapshot only — cannot show how things change over time |
| Case Reports / Anecdotal Evidence | Individual patient stories or small case series reported by clinicians. | Can generate hypotheses and identify new uses | Not generalizable; heavily subject to bias |
| Systematic Review / Meta-Analysis | Researchers analyze the combined results of many individual studies. Example: the JAMA/UCLA review. | Strongest form of evidence when based on high-quality RCTs | Only as good as the studies it includes |
Most of the cannabis evidence that currently exists falls in the middle of this hierarchy — observational studies, cohort studies, and surveys. These are valuable and should not be dismissed, but they are not the same as RCTs. When someone says "a study showed that cannabis helps with X," the first question you should ask is: what kind of study?
How This Is Changing
The good news is that the landscape is shifting — rapidly.
Exponential Growth in Research
The number of published cannabis research studies grew for the fifth consecutive year in 2025, with over 4,000 scientific papers published.
National Organization for the Reform of Marijuana Laws (NORML)
The volume of cannabis research is now growing at an unprecedented pace. Over 4,000 scientific papers on cannabis were published in 2025 alone — the fifth consecutive year of growth. This means we are learning more about cannabis right now than at any other point in history.
Regulatory Shifts
- Additional research sources: The DEA has approved new cannabis growers for research, ending the University of Mississippi monopoly and allowing studies with products that better reflect what patients actually use.
- Federal rescheduling in progress: The federal government is actively working to move cannabis from Schedule I to Schedule III. In August 2023, HHS recommended the reclassification based on scientific and medical evaluation. The DOJ issued a proposed rule in May 2024, and in December 2025, President Trump signed an executive order directing the attorney general to expedite the process. If completed, Schedule III classification would dramatically reduce the regulatory burden on cannabis researchers — eliminating the need for the special DEA licenses, expanded source requirements, and bureaucratic hurdles that have blocked large-scale studies for decades.
- State-funded research: Several states with legal cannabis programs have created their own research funding mechanisms, bypassing some of the federal restrictions.
- International research: Countries including Canada, Israel, the Netherlands, and Australia have invested heavily in cannabis research, contributing a growing body of evidence that was not possible when the U.S. dominated the research landscape.
Rescheduling Update
As of early 2026, the federal rescheduling of cannabis from Schedule I to Schedule III is actively underway, with a presidential executive order mandating acceleration of the process. If completed, this would be the single most significant change for cannabis research since the Controlled Substances Act of 1970. Schedule III substances face far fewer research restrictions, which could open the door to the large-scale, federally funded clinical trials that have been effectively blocked for over 50 years.
More Rigorous Study Designs
Newer cannabis studies are increasingly using stronger methodologies. More RCTs are underway than ever before, sample sizes are growing, and researchers are developing better ways to address the placebo challenge unique to cannabis studies. Visit our Clinical Trials page to see what is currently being studied.
Media Literacy: How Headlines Overstate Findings
One of the biggest challenges in cannabis education is the gap between what studies actually find and what media headlines claim they find. This applies in both directions:
Overstating Benefits
You will regularly see headlines like "Study Proves Cannabis Cures Anxiety" or "Cannabis Is More Effective Than Opioids for Pain." In almost every case, the actual study said something far more nuanced. A study might have found that participants reported reduced anxiety in a small survey — which is genuinely interesting but very different from "proving" anything.
Overstating Risks
Conversely, you will see headlines like "Cannabis Causes Psychosis" or "Marijuana Use Linked to Heart Attacks." These headlines often describe associations found in observational studies — which is not the same as proving causation. The actual study might have found that people with existing risk factors who used very high doses of cannabis had slightly elevated rates of a given condition.
How to Read Cannabis News Critically
- What kind of study was it? An RCT? A survey? A mouse study? Animal and cell studies are important for generating hypotheses, but they do not tell us how cannabis works in humans.
- How many people were involved? A study with 50 participants is interesting; a study with 5,000 is more convincing.
- Who funded it? Studies funded by cannabis companies may have different incentives than those funded by independent institutions. This does not automatically invalidate them, but it is worth knowing.
- Does the headline match the conclusion? Read past the headline. Often the study's actual conclusion is far more cautious than the headline suggests.
- Was it peer-reviewed? Studies published in peer-reviewed journals have been evaluated by other scientists before publication. Press releases, preprints, and company-sponsored white papers have not.
Being an Informed Consumer
At TryCannabis.org, we believe you deserve access to honest information — which means telling you not just what the research says, but how strong that research is. Throughout this site, we use the following approach:
- We always tell you what type of evidence supports any claim we make (RCT, cohort study, survey, expert opinion, etc.)
- We use evidence badges to indicate the strength of available evidence:
- Strong Evidence — supported by multiple RCTs or high-quality systematic reviews
- Moderate Evidence — supported by cohort studies, well-designed observational research, or limited RCTs
- Limited Evidence — supported primarily by surveys, case reports, or preclinical research
- Insufficient Evidence — not enough research exists to draw meaningful conclusions
- Mixed Evidence — studies disagree or show conflicting results
- We link to original sources so you can read the research yourself
- We distinguish between "evidence shows" and "patients report" — both are valuable, but they are different
The evidence gap is real, and it matters. But it is closing faster than ever, and there is still a great deal we do know. The key is to approach cannabis information the same way you would approach any other health decision: with curiosity, critical thinking, and the guidance of a qualified healthcare provider.
For a curated collection of the most important cannabis studies, visit our Latest Studies page. For in-depth breakdowns of landmark research, see our Research Summaries.