Medical Marijuana

Twenty-three states and Washington, DC, allow the use of marijuana to treat certain medical conditions.

Medical marijuana laws differ widely from state to state. Marijuana is not approved by the US Food and Drug Administration (FDA) to treat any medical condition. A drug must be carefully studied in many people before it can be approved by the FDA. There have not been enough large studies of marijuana to definitively show that it is a safe and effective drug.

But scientific study of the medical uses of marijuana is ongoing. So far, evidence suggests that marijuana may be an effective treatment for chronic pain, neuropathic (nerve) pain, and muscle spasms due to multiple sclerosis or paraplegia. In most states with medical marijuana laws, marijuana can be used to treat severe or chronic pain and severe or persistent muscle spasms.

Some states allow marijuana to be used to treat other conditions, such as glaucoma, seizures, and posttraumatic stress disorder. Every state with medical marijuana laws has its own list of approved conditions.

The active ingredients in marijuana are chemicals called cannabinoids. Marijuana preparations differ in their cannabinoid composition and consequently in their effectiveness. Two synthetic cannabinoids, dronabinol and nabilone, are available in pill form. These drugs are FDA approved and available by prescription. They are used in some patients to treat nausea and vomiting due to chemotherapy. Dronabinol is also used to treat loss of appetite and weight loss in patients with HIV/AIDS or cancer.

Cannabinoids affect areas throughout the body, but they mostly affect the central nervous system (brain and spinal cord). The main chemical in marijuana that causes intoxication is tetrahydrocannabinol (THC). Another cannabinoid of medical interest is cannabidiol (CBD), which does not cause intoxication.

Effects of marijuana can include reduction in pain, nausea, vomiting, and muscle spasms as well as increased appetite. Common side effects include dizziness, dry mouth, nausea, disorientation, euphoria, confusion, and sedation.

Marijuana, like all drugs, has potential risks. It causes an increase in heart rate, which may increase the chance of heart attack in people who are already at risk. Regular smoking of marijuana is associated with breathing problems such as cough and increased risk of lung infections. It can also be addicting and can interfere with work, school, and relationships.

Under federal law, marijuana has no currently accepted medical use and has a high potential for abuse. For these reasons, doctors cannot prescribe marijuana. In a state that allows the use of marijuana to treat medical conditions, however, a doctor may be able to certify its use. Your state may require you to apply for a state-issued identification card to use medical marijuana.

Marijuana can be used in different ways. It can be smoked, mixed into foods, and brewed as tea. Dosing of marijuana is not straightforward and depends on the patient, the preparation, and the way the drug is used. Talk to your doctor if you have questions about using medical marijuana.

Sources: National Institute on Drug Abuse

Hill KP. Medical marijuana for treatment of chronic pain and other medical and psychiatric problems: a clinical review. JAMA. doi: 10.1001/jama.2015.6199.

Whiting PF, Wolff RF, Deshpande S, et al. Cannabinoids for medical use: a systematic review and meta-analysis. JAMA. doi: 10.1001/jama.2015.6358.

Topic: Medications