Medical Marijuana

Medically Reviewed by Arefa Cassoobhoy, MD, MPH on November 04, 2013

More states are passing laws that allow people to use medical marijuana. So what does it treat, and who can and should use it?

Pain is the main reason people ask for a prescription, says Barth Wilsey, MD, a pain medicine specialist at the University of California Davis Medical Center. It could be from headaches, a disease like cancer, or a long-term condition, like glaucoma or nerve pain.

If you live in a state where medical marijuana is legal and your doctor thinks it would help, you’ll get a “marijuana card.” You will be put on a list that allows you to buy marijuana from an authorized seller, called a dispensary.

Doctors also may prescribe medical marijuana to treat:

The FDA has also approved THC, a key ingredient in marijuana, to treat nausea and improve appetite. It's available by prescription Marinol (dronabinol) and Cesamet (nabilone).

Your body already makes marijuana-like chemicals that affect pain, inflammation, and many other processes. Marijuana can sometimes help those natural chemicals work better, says Laura Borgelt, PharmD, of the University of Colorado.

Medical marijuana may be:

  • Smoked
  • Vaporized (heated until active ingredients are released, but no smoke is formed)
  • Eaten (usually in the form of cookies or candy)
  • Taken as a liquid extract

Side effects of marijuana that usually don’t last long can include:

More serious side effects include severe anxiety and psychosis.

Medical marijuana is not monitored like FDA-approved medicines. When using it, you don’t know its potential to cause cancer, its purity, potency, or side effects.

Only people who have a card from a doctor should use medical marijuana. Doctors will not prescribe medical marijuana to anyone under 18. Others who should not use it:

  • People with heart disease
  • Pregnant women
  • People with a history of psychosis

Show Sources


Barth Wilsey, MD, associate physician, Department of Medicine & Physical Rehabilitation, University of California Davis Medical Center.

Laura Borgelt, PharmD, associate professor, Departments of Clinical Pharmacy and Family Medicine, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of Colorado.

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