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Medical marijuana

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, about half of the states have legalized marijuana for medical use.

How Does Medical Marijuana Work?

Medical marijuana may be:

  • Smoked
  • Vaporized
  • Eaten
  • 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
  • Epilepsy

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 doctor 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:

  • Cancer
  • HIV/AIDS
  • Seizures and epilepsy
  • Glaucoma
  • Severe chronic pain
  • Severe nausea
  • Extreme weight loss and weakness (wasting syndrome)
  • Severe muscle spasms
  • Multiple sclerosis

Side Effects

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

Who Should not use Medical Marijuana?

Doctors 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 2 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.

Alternative Names

Pot; Grass; Cannabis; Weed; Hash; Ganja

References

American Academy of Neurology. Medical Marijuana in Certain Medical Disorders. www.aan.com/Guidelines/Home/GetGuidelineContent/650. Accessed August 24, 2015.

American Cancer Society. Marijuana. www.cancer.org/treatment/treatmentsandsideeffects/complementaryandalternativemedicine/herbsvitaminsandminerals/marijuana. Accessed August 24, 2015.

Gerich. M, Isfort, R, Brimhall, B, and Siegel, C. Medical marijuana for digestive disorders: High time to prescribe? Am J Gastroenrerol. 2014. PMID: 25199471 www.ncbi.nlm.nih.gov/pubmed/25199471.

Lutge EE, Gray A, Siegfried N. The medical use of cannabis for reducing morbidity and mortality in patients with HIV/AIDS. Cochrane Database Syst Rev. 2013;4:CD005175. PMID: 23633327 www.ncbi.nlm.nih.gov/pubmed/23633327.

Naftali T, Bar-Lev Schleider L, Dotan I, Lansky EP, Sklerovsky Benjaminov F, Konikoff FM. Cannabis induces a clinical response in patients with Crohn's disease: a prospective placebo-controlled study. Clin Gastroenterol Hepatol. 2013;11(10):1276-80.e1. PMID: 23648372 www.ncbi.nlm.nih.gov/pubmed/23648372.

Naftali T, Mechulam R, Lev LB, Konikoff FM. Cannabis for inflammatory bowel disease. Dig Dis. 2014;32(4):468-74. PMID: 24969296 www.ncbi.nlm.nih.gov/pubmed/24969296.

National Cancer Institute. Summary of the Evidence for Cannabis and Cannabinoids. www.cancer.gov/cancertopics/pdq/cam/cannabis/healthprofessional/page7. Accessed August 24, 2015.

National Center for Complementary and Integrative Health. Medical Marijuana. nccih.nih.gov/health/marijuana. Accessed August 24, 2015.

National Institute on Drug Abuse. Is Marijuana Medicine? www.drugabuse.gov/publications/drugfacts/marijuana-medicine. Accessed August 24, 2015.

Review Date 9/8/2015

Updated by: Laura J. Martin, MD, MPH, ABIM Board Certified in Internal Medicine and Hospice and Palliative Medicine, Atlanta, GA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.

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