Marijuana is best known as a drug that people smoke or eat to get high. It is derived from the plant Cannabis sativa. Possession of marijuana is illegal under federal law. Medical marijuana refers to using marijuana to treat certain medical conditions. In the United States, over one half of the states have legalized marijuana for medical use.
How Does Medical Marijuana Work?
Medical marijuana may be:
- Taken as a liquid extract
Marijuana leaves and buds contain substances called cannabinoids. THC is a cannabinoid that can affect the brain and change your mood or consciousness.
Different varieties of marijuana contain different amounts of cannabinoids. This sometimes makes the effects of medical marijuana hard to predict or control. The effects also may differ depending on whether it is smoked or eaten.
What Conditions Can It Help?
Medical marijuana may be used to:
- Ease pain. This includes different types of chronic pain, including pain from nerve damage.
- Control nausea and vomiting. The most common use is for nausea and vomiting caused by chemotherapy for cancer.
- Make a person feel like eating. This helps people who do not eat enough and lose weight due to other illnesses, such as HIV/AIDS and cancer.
Some small studies show that marijuana might relieve symptoms in people who have:
- Multiple sclerosis
- Crohn disease
- Inflammatory bowel disease
Smoking marijuana lowers pressure inside the eyes, a problem linked to glaucoma. But the effect does not last long. Other glaucoma medicines may work better to treat the disease.
How Do People Get Medical Marijuana?
In states where medical marijuana is legal, you need a written statement from your health care provider to get the drug. It must explain that you need it to treat a medical condition or to ease side effects. Your name will be put on a list that lets you buy marijuana from an authorized seller.
What Medical Conditions Qualify?
You can only get medical marijuana if you have certain conditions. The conditions marijuana can treat varies from state to state. The most common ones include:
- Seizures and epilepsy
- Severe chronic pain
- Severe nausea
- Extreme weight loss and weakness (wasting syndrome)
- Severe muscle spasms
- Multiple sclerosis
Possible physical symptoms from using marijuana include:
- A fast or irregular heartbeat
- Slow reaction times
Possible mental or emotional side effects include:
- A strong feeling of happiness or well-being
- Short-term memory loss
- Trouble concentrating
- Decreased or increased anxiety
Who Should Not Use Medical Marijuana?
Providers are not allowed to prescribe medical marijuana to people younger than age 18. Other people who should not use medical marijuana include:
- People with heart disease
- Pregnant women
- People with a history of psychosis
Other concerns linked to marijuana use include:
- Dangerous driving or other risky behaviors
- Lung irritation
- Dependence or addiction to marijuana
Prescription Drugs Based on Marijuana Compounds
The US Food and Drug Administration (FDA) has not approved marijuana for treating any health conditions.
However, the FDA has approved two prescription medicines that contain man-made cannabinoids.
- Dronabinol (Marinol). This drug treats nausea and vomiting caused by chemotherapy and loss of appetite and weight loss in people with HIV/AIDS.
- Nabilone (Cesamet). This drug treats nausea and vomiting caused by chemotherapy in people who have not had relief from other treatments.
Unlike medical marijuana, the active ingredient in these drugs can be controlled, so you always know how much you get in a dose.
Pot; Grass; Cannabis; Weed; Hash; Ganja
American Cancer Society website. Marijuana and cancer. www.cancer.org/treatment/treatments-and-side-effects/complementary-and-alternative-medicine/marijuana-and-cancer.html. Updated March 16, 2017. Accessed October 15, 2019.
Fife TD, Moawad H, Moschonas C, Shepard K, Hammond N. Clinical perspectives on medical marijuana (cannabis) for neurologic disorders. Neurol Clin Pract. 2015;5(4):344-351. PMID: 26336632 www.ncbi.nlm.nih.gov/pubmed/26336632.
Halawa OI, Furnish TJ, Wallace MS. Role of cannabinoids in pain management. In: Benzon HT, Raja SN, Liu SS, Fishman SM, Cohen SP, eds. Essentials of Pain Medicine. 4th ed. Philadelphia, PA: Elsevier; 2018:chap 56.
National Academies of Sciences, Engineering, and Medicine; Health and Medicine Division; Board on Population Health and Public Health Practice; Committee on the Health Effects of Marijuana: An Evidence Review and Research Agenda. The Health Effects of Cannabis and Cannabinoids: The Current State of Evidence and Recommendations for Research. Washington, DC: National Academies Press; 2017.
National Cancer Institute website. Cannabis and cannabinoids (PDQ) - health professional version. www.cancer.gov/about-cancer/treatment/cam/hp/cannabis-pdq#section/all. Updated July 16, 2019. Accessed October 15, 2019.
Review Date 9/16/2019
Updated by: Linda J. Vorvick, MD, Clinical Associate Professor, Department of Family Medicine, UW Medicine, School of Medicine, University of Washington, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.