What is medical cannabis used for?
Medical cannabis is used to relieve symptoms that do not respond well to standard treatment. The three uses with the strongest research support are chronic pain, chemotherapy-induced nausea and vomiting, and muscle spasticity from multiple sclerosis.
Doctors and state programs also recognize it for severe childhood epilepsy, sleep problems, appetite loss, and some anxiety or PTSD symptoms. Relief comes from cannabinoids, mainly THC and CBD, which interact with the body's endocannabinoid system.
Which conditions have the strongest evidence?
Chronic pain
Chronic pain is the most common reason people seek medical cannabis. Reviews of clinical trials show modest but real reductions in neuropathic and musculoskeletal pain, often when opioids or other drugs have not worked well enough.
Nausea and vomiting from chemotherapy
Cannabinoids reduce nausea and vomiting triggered by cancer treatment, which is why synthetic THC drugs were approved for this use decades ago. Patients who do not respond to standard anti-nausea medications are the typical candidates.
Multiple sclerosis spasticity
Muscle tightness and spasms in multiple sclerosis respond to THC-dominant preparations. Patients report less stiffness and fewer painful spasms, though the effect is moderate rather than dramatic.
Rare childhood epilepsy
Purified CBD reduces seizure frequency in Dravet syndrome and Lennox-Gastaut syndrome, two severe forms of childhood epilepsy. This is the best-documented pediatric use and the basis of the only FDA-approved cannabis-derived seizure medication.
What else do patients use medical cannabis for?
State qualifying condition lists often include several additional diagnoses. Evidence for these ranges from promising to preliminary.
- Sleep disturbances and insomnia
- Appetite loss and weight loss from illness
- Anxiety disorders and post-traumatic stress disorder
- Crohn's disease and inflammatory bowel symptoms
- Glaucoma, mainly as a historical use since effects are short lived
- Migraine and tension headaches
- Cachexia and wasting syndrome
How does medical cannabis work in the body?
THC binds CB1 receptors in the brain and nervous system, which shapes pain perception, mood, appetite, and sleep. CBD does not produce a high and appears to calm inflammation and seizure activity through other pathways.
Effects depend on the dose, the THC-to-CBD ratio, and the route of administration. Inhaled products act within minutes, while edibles and tinctures can take one to two hours to peak.
Is medical cannabis FDA approved?
The FDA has not approved the cannabis plant itself for any medical use. It has approved purified cannabinoid drugs instead: Epidiolex, a CBD product for certain seizures, plus dronabinol and nabilone, which are synthetic THC products for nausea and appetite stimulation.
Everything else sold in dispensaries is regulated at the state level, not by the FDA. That means testing standards, labeling, and product quality vary from state to state.
How do you get medical cannabis legally in the US?
Medical cannabis is regulated by individual states. A licensed physician certifies that you have a qualifying condition, then you register with the state program and purchase from a licensed dispensary.
Qualifying condition lists, possession limits, and home-grow rules differ by state. Some states also allow recreational sales, but medical patients often pay lower taxes and can access higher-dose or higher-CBD products.
What are the risks and side effects?
Common side effects include drowsiness, dizziness, dry mouth, impaired short-term memory, and a faster heartbeat. These are more likely with high THC doses and in people who are new to cannabis.
Serious considerations include dependence, interactions with sedatives and blood thinners, and an increased risk of psychosis in people who are predisposed to it. Inhaled cannabis also carries the same lung irritation risks as smoking.
Do not drive after use, and tell your doctor about every other medication you take.
Frequently asked questions
Does medical cannabis cure disease?
No. It manages symptoms such as pain, nausea, and spasms. It does not treat or reverse the underlying condition.
What is the difference between medical and recreational cannabis?
It is the same plant. The difference is the legal pathway: medical use requires a physician certification and state registration, while recreational use does not.
Can a doctor prescribe medical cannabis?
Doctors in most medical states certify or recommend it rather than write a standard prescription. That distinction exists because federal law still classifies cannabis as a controlled substance.
How long does it take to feel effects?
Inhaled products work in about five to ten minutes. Edibles and tinctures typically take 30 minutes to two hours, and effects last longer, so start with a low dose.