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JAMA Internal Medicine Patient Page
February 11, 2020

What Should I Know About Medical Cannabis?

JAMA Intern Med. 2020;180(4):624. doi:10.1001/jamainternmed.2020.0018

What Is Cannabis and How Is It Used?

  • Cannabis (ie, marijuana) is a plant that contains a complex mixture of chemicals called cannabinoids. Examples of cannabinoids include tetrahydrocannabinol (THC) and cannabidiol (CBD).

  • Whereas THC is primarily responsible for the psychoactive effects (euphoria) of cannabis, CBD may decrease pain but causes far fewer psychoactive effects than THC.

  • Cannabis is used medically as purified cannabinoids (eg, CBD), synthetic cannabinoids (eg, dronabinol), or parts of the whole plant.

  • Cannabinoids are typically smoked or vaporized; ingested as pills, tinctures, oils, or edibles; or applied to the skin as creams or patches.

How Is Cannabis Regulated in the United States?

Most states have legalized cannabis use for medical conditions. Some states have legalized cannabis for recreational adult use. The federal government considers cannabis use to be illegal. However, clinicians and patients who act in accord with state laws on medical use of cannabis are not likely to be federally prosecuted. Typically, cannabis contents, potency, and safety are not regulated by the government even in states where it is legal.

Are There Proven Benefits to Using Medical Cannabis?

Patients with spasticity related to multiple sclerosis, rare forms of childhood epilepsy, or nausea associated with chemotherapy have been shown to benefit from medical use of specific cannabinoids. Substantial evidence demonstrates that cannabis helps to modestly reduce pain. The most consistent benefit is seen in nerve pain. Cannabis is often portrayed as a treatment for conditions like anxiety, opioid addiction, and insomnia. There is not conclusive evidence to know if it helps with these conditions.

Is Using Cannabis Dangerous?

No deaths have been conclusively linked to cannabis or cannabinoid overdose. However, there are some risks associated with cannabis use even for medical purposes. Cannabis acutely impairs memory, judgment, and motor skills. Driving under the influence of cannabis affects driving ability. It may be associated with an increased risk of automobile accidents. Deaths from vaping-associated lung illness have been reported in some individuals using vaped cannabis product. It is not clear what role cannabis plays in this illness. Cannabis can be habit forming over time and lead to unhealthy use. Long-term daily use, starting at a young age, and using large amounts may be associated with negative social and health consequences. Smoking cannabis over time is associated with chronic breathing problems. These often improve after stopping. Frequent cannabis use during adolescence is associated with increased risk of developing long-term psychiatric conditions. Cannabis use during pregnancy is associated with low birth weight and other complications. More study must be done to fully understand if there is an association of lung cancer or heart disease with smoking cannabis.

How Can My Doctor Help Me?

  • Open communication with your clinician will help you have a better understanding of the potential benefits and risks of cannabis use based on your medical history and current medications.

  • Talk to your clinician about why you think you would benefit from cannabis. There may be other effective ways to address your health concerns.

  • Your clinician can inform you how to legally obtain cannabis in your state.

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Section Editor: Michael Incze, MD, MSEd.
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Article Information

Published Online: February 11, 2020. doi:10.1001/jamainternmed.2020.0018

Conflict of Interest Disclosures: Dr Slawek reported grants from the National Institutes of Health during the conduct of the study. No other disclosures were reported.

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    2 Comments for this article
    Labelling laws and over the counter CBD oils
    Katherine White, MA (Hons), ACIS | University of Würzburg, Department of Political Science and Sociology
    To my frustration, one of the underrecognized problems with current licensing of over the counter CBD products arises from cross-contamination. A bottle of low strength (2.75%) CBD oil purchased through a retail high street vitamin and health food products store gave me a nasty gluten reaction with an extremely itchy dermatitis herpetiformis rash. A self-conducted skin prick test confirmed the source of the gluten reaction.

    I had been taking around half the recommended daily maximum dose of this brand of CBD oil to ease inflammatory spinal arthritis symptoms, to see if this would help me reduce my use of
    prescribed opiate pain relief. It worked for transitory pain relief - but one of the side effects of a gluten reaction is, for me, an increase in peripheral joint pain. Not so good.

    Surely the same labelling standards should apply to over-the-counter supplements as for ordinary food products, ie a warning that a product may contain trace gluten or other factory cross-contamination?
    FDA Warnings Regarding Marijuana Use During Pregnancy, Breastfeeding and Around Children
    DAVID KELLER, M.S., M.D. | Internal Medicine Physician
    The Food and Drug Administration (FDA) website warns as follows:

    "There are many potential negative health effects from using marijuana and other products containing THC during pregnancy and while breastfeeding. In fact, the U.S. Surgeon General recently advised consumers that marijuana use during pregnancy may affect fetal brain development, because THC can enter the fetal brain from the mother’s bloodstream. The Surgeon General also advised that marijuana may increase the risk of a newborn with low birth weight. Research also suggests increased risk for premature birth and potentially stillbirth.

    "While breastfeeding, it is important to know that breastmilk
    can contain THC for up to six days after use. This THC may affect a newborn’s brain development and result in hyperactivity, poor cognitive function, and other long-term consequences.

    "Additionally, marijuana smoke contains many of the same harmful components as tobacco smoke. Neither marijuana nor tobacco products should be smoked around a baby or children."

    Reference: FDA website, accessed on April 7, 2020 at 6 am, at the following URL: