420: Medical Cannabis Research Hub
Medical cannabis is one of the fastest-moving areas of health research. This hub sums up what the strongest evidence shows, which cannabinoid medicines are approved, how patients get access in Canada and the US, what the risks are and where to find trustworthy research.
Important
What the strongest evidence shows
- Conclusive: nausea and vomiting from chemotherapy
The US National Academies found conclusive evidence that oral cannabinoids (THC-based medicines) are effective against chemotherapy-induced nausea and vomiting.
- Substantial: chronic pain in adults
Some cannabis products are effective for chronic pain in adults, according to the same 2017 review of more than 10,000 studies.
- Substantial: multiple sclerosis spasticity
Oral cannabinoids such as nabiximols and nabilone improve muscle spasticity reported by people with multiple sclerosis.
- Proven in trials: rare forms of epilepsy
Purified cannabidiol (CBD) reduces seizures in Lennox-Gastaut syndrome, Dravet syndrome and tuberous sclerosis complex, which is why the FDA approved Epidiolex.
- Still uncertain
For anxiety, sleep, PTSD, inflammatory bowel disease and many other conditions, the evidence is limited, mixed or of low quality. Better trials are under way.
Approved cannabinoid medicines
Approved by the US FDA on June 25, 2018, for seizures in Lennox-Gastaut and Dravet syndromes; tuberous sclerosis complex was added later. The first FDA-approved drug made from the cannabis plant.
A THC and CBD mouth spray approved by Health Canada on April 19, 2005, first for nerve pain in multiple sclerosis. Used in many countries for MS spasticity.
Synthetic THC and a THC-like drug, approved since the 1980s for chemotherapy nausea, and dronabinol also for appetite loss in AIDS.
How access works
Canada. Since the Cannabis Act came into force on October 17, 2018, patients authorized by a health care practitioner can buy from a federally licensed seller, register with Health Canada to grow a limited amount for themselves, or designate someone to grow it for them. Patients can carry the lesser of 150 grams or a 30-day supply of dried cannabis in public. See Health Canada.
United States. Cannabis is legal for medical use in most states, but federal law is changing. On April 28, 2026, the Department of Justice moved FDA-approved marijuana medicines and state-licensed medical marijuana products to Schedule III. A broader move of all marijuana to Schedule III is still before a DEA administrative law judge, with written briefs due in late October and early November 2026. See the DEA’s rescheduling page.
Known risks
- Driving
Recent cannabis use is linked to a higher risk of motor vehicle crashes. Do not drive while impaired.
- Mental health
Cannabis use is associated with psychosis and schizophrenia, with the highest risk among the most frequent users and people with a family history.
- Pregnancy
Smoking cannabis during pregnancy is linked to lower birth weight. Health authorities advise against cannabis use while pregnant or breastfeeding.
- Problem use
Starting young raises the risk of developing cannabis use disorder.
- Lungs
Long-term smoking is linked to cough, wheezing and chronic bronchitis. Non-smoked forms avoid smoke exposure.
- Drug interactions
CBD and THC can interact with other medicines, including some anti-seizure drugs and blood thinners. Ask a pharmacist.
Directory: top medical cannabis research sites
How patients access medical cannabis in Canada under the Cannabis Act: medical documents, licensed sellers and personal production.
Canada · GovernmentHealth Canada: Information for health care professionalsHealth Canada’s detailed clinical monograph on cannabis and the cannabinoids, with dosing, interactions and evidence by condition.
Canada · ClinicalCanada’s Drug Agency (CDA-AMC): CannabisIndependent evidence reviews on medical cannabis from Canada’s national drug and health technology agency.
Canada · Evidence reviewsCanadian Consortium for the Investigation of CannabinoidsA Canadian non-profit that supports cannabinoid research and offers education for health care professionals.
Canada · Research networkCanadian Medical Association: Cannabis facts and resourcesThe CMA’s cannabis resources for clinicians and patients.
Canada · Medical associationNational Academies: The Health Effects of Cannabis and CannabinoidsThe landmark 2017 review of more than 10,000 studies, grading the evidence for benefits and harms. Free to read online.
United States · Evidence reviewNIDA: Cannabis (marijuana)The US National Institute on Drug Abuse’s research summaries on cannabis, including risks and cannabis use disorder.
United States · GovernmentNCCIH: Cannabis and cannabinoidsData on NIH-funded research into cannabis, cannabinoids and related compounds, with links to studies.
United States · Research fundingCenter for Medicinal Cannabis Research (UC San Diego)One of the longest-running university centres running clinical trials of cannabis for pain, spasticity and other conditions.
United States · UniversityLambert Initiative for Cannabinoid Therapeutics (University of Sydney)A major research centre on cannabinoid medicines, from lab science to clinical trials.
Australia · UniversityEUDA: Medical use of cannabis and cannabinoidsThe European Union Drugs Agency’s review of the evidence and of medical cannabis laws in Europe.
Europe · GovernmentDrug Science: Project Twenty21The UK’s largest medical cannabis patient registry, collecting real-world outcome data.
United Kingdom · Patient registryInternational Cannabinoid Research SocietyThe leading scientific society for cannabinoid researchers, with an annual symposium.
International · Scientific societyInternational Association for Cannabinoid MedicinesAn association of physicians and scientists that publishes news and reviews on cannabinoid medicine.
International · Medical associationPubMed: Medical cannabis researchSearch millions of peer-reviewed biomedical papers. Filter by systematic review or clinical trial for the strongest evidence.
Search · StudiesClinicalTrials.gov: Cannabis trialsFind completed and recruiting clinical trials of cannabis and cannabinoids worldwide.
Search · TrialsHow to read cannabis research
- Prefer systematic reviews and randomized trials over single studies, surveys or anecdotes.
- Check what was tested. A purified CBD medicine, a THC spray and smoked flower are very different products.
- Look at the dose and the comparison. Was it compared with a placebo or an existing treatment?
- Check who paid for it. Industry funding is common and should be disclosed.
- Separate association from cause. Many harm findings show a link, not proof that cannabis caused the outcome.
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Questions
Is medical cannabis effective?
For some conditions, yes. The strongest evidence supports chemotherapy-induced nausea and vomiting, chronic pain in adults, multiple sclerosis spasticity and certain rare forms of epilepsy. For many other conditions the evidence is still limited.
What is the difference between CBD and THC?
THC is the main intoxicating compound in cannabis. CBD does not cause a high and is the active ingredient in Epidiolex, an approved epilepsy medicine.
How do I get medical cannabis in Canada?
You need a medical document from a health care practitioner. You can then register with a federally licensed seller, or register with Health Canada to grow a limited amount yourself or have someone grow it for you.
Is cannabis legal federally in the United States?
Partly. Since April 2026, FDA-approved marijuana medicines and state-licensed medical marijuana are in Schedule III. A broader rescheduling of marijuana is still under review by the DEA.
Why is this page called 420?
420 is a long-standing nickname for cannabis culture. This page uses it as a short, memorable address for serious research.
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