Medically Reviewed by Jabeen Begum, MD on January 09, 2024
Written by Stephanie Watson, Kim Painter
- What Is Medical Marijuana?
- What Is Medical Marijuana Used For?
- Benefits of Medical Marijuana
- Medical Marijuana Side Effects
9 min read
What Is Medical Marijuana?
Medical marijuana, or medical cannabis, uses the cannabis plant or chemicals in it to treat symptoms or conditions. Medical marijuana mostly comes in the same forms as recreational marijuana, but there also are highly purified and lab-made versions used for certain conditions.
The cannabis plant contains more than 100 different chemicals called cannabinoids. Each one has a different effect on the body. Delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD) are the main chemicals used in medicine. THC also produces the “high” people feel when they smoke marijuana or eat foods containing it.
As of 2023, a broad range of medical marijuana products were legal in 38 states, three territories, and the District of Columbia but remained illegal under federal law.
What Is Medical Marijuana Used For?
States where medical marijuana is legal have approved it for a varying list of conditions. Depending on where you live, these might include:
- Severe and chronic pain
- Multiple sclerosis and muscle spasms
- Severe nausea and vomiting caused by cancer treatment
- Epilepsy and seizures
- Alzheimer’s disease
- Amyotrophic lateral sclerosis (ALS)
- HIV/AIDS
- Crohn’s disease
- Glaucoma
- Migraine
- Anorexia
- Extreme weight loss and weakness (wasting syndrome)
- Irritable bowel syndrome
- Post-traumatic stress disorder
It is important to know that many of the uses that states allow aren’t backed by strong scientific evidence. This is partly because researchers find it hard to do studies on a drug that remains illegal under federal law, even when it’s allowed by states.
It’s also important to realize that cannabis is almost always used to treat symptoms — like the muscle spasms of multiple sclerosis and the loss of appetite caused by HIV drugs — rather than the conditions themselves.
Medical Marijuana: What Does It Treat?
More and more states are legalizing marijuana to treat pain and illness. Find out what conditions it’s used for and the known side effects.
Medical Marijuana: What Does It Treat?
Benefits of Medical Marijuana
Cannabinoids, the active chemicals in medical marijuana, are similar to chemicals the body makes that are involved in appetite, memory, movement, and pain.
So far, solid studies suggest that these chemicals can:
- Control vomiting in people undergoing cancer chemotherapy. Drugs based on two lab-made forms of THC are FDA-approved for this purpose.
- Modestly reduce pain in people with conditions such as nerve damage, cancer, multiple sclerosis, and rheumatoid arthritis.
- Reduce muscle spasms in people with multiple sclerosis. (There’s less evidence it helps muscle spasms in people with spinal cord injuries).
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In addition, there’s some evidence that medical marijuana might:
- Improve sleep in the short term for people with obstructive sleep apnea, fibromyalgia, chronic pain, or multiple sclerosis.
- Increase appetite and decrease weight loss in people with HIV and AIDS.
- Reduce tics in people with Tourette’s syndrome.
- Reduce anxiety in people with social anxiety disorder.
- Improve symptoms of post-traumatic stress disorder.
There’s not enough evidence to say whether medical marijuana works or not for many other conditions, including irritable bowel syndrome, Parkinson’s disease, and addiction to other substances.
In some cases, the limited evidence available suggests it doesn’t help. That’s the case with Alzheimer’s and other forms of dementia. That’s also the case with glaucoma, an eye disease that can be caused by increased pressure in the eyes. Marijuana might lower the pressure briefly, but not as long as effective drugs do.
Can medical marijuana help with seizure disorders?
Medical marijuana received a lot of attention a few years ago when parents said that a special form of the drug helped control seizures in their children. Studies showed good enough results for the FDA to approve Epidiolex, made from a purified form of CBD, as a therapy for people with two rare seizure disorders, Lenox-Gastaut and Dravet syndromes.
There’s no approved form of medical marijuana for people with more common forms of epilepsy. Studies looking at broader uses are underway.
Medical Marijuana Side Effects
Medical marijuana can cause harm. The most serious harms include an increased risk of car crashes in intoxicated users and the risk that children might accidentally ingest these products and have breathing problems and other overdose symptoms. Adults over age 65 may also face an increased risk of injury when using marijuana.
Other short-term effects, including some that people enjoy and others that cause distress, can include:
- Euphoria, which means a strong sense of happiness or well-being
- Altered senses, such as seeing brighter colors or smelling stronger odors
- An altered sense of space and time
- Impaired memory and thinking
- Confusion and disorientation
- Poor muscle coordination
- Relaxation or sleepiness
- Dizziness
- Panic attacks
- Dry mouth
- Increased heart rate
- Increased appetite
- Slower reaction times
- Harmful interactions with other drugs
- Hallucinations (seeing things that aren’t there) or delusions (believing things that aren’t true). These tend to occur only at high doses.
Marijuana also may have long-term effects, including:
- Negative effects on attention, learning, and memory in teens and young adults who use a lot of marijuana before their brains are fully developed.
- Harms linked to smoking. Any kind of smoking can damage your lungs and increase your risk of stroke, heart disease, and blood vessel disease.
- An increased risk of schizophrenia in people already at risk for this serious mental health disorder.
- Frequent, severe vomiting, among longtime users of high-dose THC.
- Addiction (cannabis use disorder). This is more likely to happen among teens than among adult users.
People who should not use marijuana include:
- Those who are pregnant. THC can get into the fetal brain and affect later attention, memory, and problem-solving. Marijuana also can increase the risk of stillbirth, premature birth, and low birth weight.
- Those who are breastfeeding. THC can also get into infant brains and may harm development.
Researchers say marijuana could also be dangerous for:
- People with a history of psychosis, whose condition may get worse.
- People with heart disease. Smoked marijuana, in particular, has clear heart risks. Studies find an increased risk of heart attack in the hour after smoking marijuana.
There are other safety issues to consider. The National Institute on Drug Abuse says marijuana can be addictive and is considered a “gateway drug” to using other drugs. But many other experts disagree. In fact, the Centers for Disease Control (CDC) states that most people who use medical marijuana do not go on to use “harder drugs” or street drugs.
Also, the FDA doesn’t oversee medical marijuana like it does prescription drugs, except purified and lab-made versions approved for certain uses. Although states monitor and regulate sales, they often don’t have the resources to do so effectively. That means the strengths and ingredients of marijuana can differ quite a bit depending on where you buy it. Products also may contain levels of active ingredients that differ from what’s on their labels. Contaminated products, with high levels of pesticides or germs, also have been reported.