Possession of marijuana is illegal under federal law. In the United States, however, over one half of the states have legalized marijuana for medical use.

Medical marijuana may be:

• Smoked
• Vaporized
• Orally consumed (capsules, edibles, tinctures)
• Placed under the tongue (sublingual)
• Place on the mucous membranes of the mouth
• Used topically
• Used rectally as a suppository

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 how it is taken.

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
• Epilepsy

Smoking marijuana lowers pressure inside the eyes. But the effect does not last long and this is not often the recommended treatment for glaucoma. Other glaucoma medicines work better to treat the disease.

In states where medical marijuana is legal, you need a written statement from your health care provider to get the medicine. 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.

You can only get medical marijuana if you have certain conditions. The conditions marijuana can be used to treat vary from state to state. The most common ones include:

• Cancer
• HIV/AIDS
• Seizures and epilepsy
• Glaucoma
• 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
• Dizziness
• Slow reaction times
• Drowsiness

Possible mental or emotional side effects include:

• A strong feeling of happiness or well-being
• Short-term memory loss
• Trouble concentrating
• Confusion
• Decreased or increased anxiety

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. Some studies have linked marijuana use with increased risk of heart attack and stroke.
• 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

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 medicine treats nausea and vomiting caused by chemotherapy and loss of appetite and weight loss in people with HIV/AIDS.
• Nabilone (Cesamet). This medicine 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 medicines can be controlled, so you always know how much you get in a dose.

Pot; Grass; Cannabis; Weed; Hash; Ganja

American Cancer Society website. Cannabis and cancer. www.cancer.org/cancer/supportive-care/integrative-medicine/cannabis.html. Updated July 11, 2025. Accessed December 12, 2025.

Arnold RM, Kutner JS. Palliative care. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 3.

Deutsch JK, Hass DJ. Complementary, alternative, and integrative medicine. In: Feldman M, Friedman LS, Brandt LJ, eds. Sleisenger & Fordtran's Gastrointestinal and Liver Disease. 11th ed. Philadelphia, PA: Elsevier; 2021:chap 131.

Gonzalez D, McCammon SD. Integrating palliative and curative care strategies in the practice of otolaryngology. In: Francis HW, Haughey BH, Hillel AT, et al, eds. Cummings Otolaryngology: Head & Neck Surgery. 8th ed. Philadelphia, PA: Elsevier; 2026:chap 80.

Mostoufi SA. Chronic pain syndrome. In: Frontera WR, Silver JK, Rizzo TD Jr, eds. Essentials of Physical Medicine and Rehabilitation: Musculoskeletal Disorders, Pain, and Rehabilitation. 4th ed. Philadelphia, PA: Elsevier; 2019:chap 98.

National Cancer Institute website. Cannabis and cannabinoids (PDQ) - health professional version. www.cancer.gov/about-cancer/treatment/cam/hp/cannabis-pdq#section/all. Updated May 13, 2025. Accessed December 12, 2025.

Updated by: Laura J. Martin, MD, MPH, ABIM Board Certified in Internal Medicine and Hospice and Palliative Medicine, Atlanta, GA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.