Dana-Farber Cancer Institute

Cannabis During Cancer Treatment

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    Scientific studies show that many people with cancer take cannabis (marijuana) to ease symptoms from cancer and its treatment. Here you’ll find trusted, research-based information on how cannabis may support your care.

    Cannabis Can Be Medicinal

    Research suggests cannabis may help manage some side effects of cancer treatment.1 For instance, it can reduce nausea and vomiting from chemotherapy when standard treatments don't work well. People also consider cannabis for help with cancer-related pain, anxiety, and sleep problems, even though science has not confirmed its usefulness. Studies suggest cannabis is not particularly helpful for weight loss during cancer, despite its reputation as an hunger stimulant. More research is needed on whether cannabis can improve these cancer-related symptoms.

    So far, most studies have focused on adults with cancer. We also need more research on cannabis as an option for helping children with cancer. Whether you are an adult or a child, talk with your cancer care team if you take cannabis or are thinking about it.

    Can Cannabis Cure Cancer?

    There is no proof that cannabis cures cancer. In fact, early research suggests some cancer treatments — such as immunotherapy —  may be less effective if you take cannabis. For this reason, we ask that you talk with your care team before taking cannabis.

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    Discussing Cannabis With Your Care Team

    About 1 in 4 adults with cancer report taking cannabis.2 Tell your Dana-Farber care team if you take cannabis or are thinking about it, just like you would report other medicines or supplements. Your team may ask about:

    • Your goals for using cannabis
    • The products you take
    • How often they are taken
    • How they affect you

    This helps us give you safe, personalized guidance.

    Meet Our Experts

    Differences Between Cannabis and Cannabinoids

    People have used the cannabis plant for thousands of years for medical and non-medical reasons. Cannabis is also called marijuana, weed, pot, or reefer.

    Cannabis contains hundreds of chemicals. Some of these are called cannabinoids. The two best-known cannabinoids are THC (delta-9-tetrahydrocannabinol) and CBD (cannabidiol).

    • THC changes how you think and feel and can cause a “high” feeling.
    • CBD can affect how you feel, but it doesn’t cause a “high” feeling or change your thinking like THC does.

    The many chemicals in cannabis, including THC and CBD, can interact in complex ways.

    How Cannabis Is Taken

    People take cannabis in different ways, and each way affects the body differently.

    Eating or Drinking (Edibles)

    Cannabis-infused foods and drinks such as gummies, brownies, and teas are common. Edibles can take 30 minutes to 2 hours to start working, and effects can last 5 to 8 hours. 

    Tip: Those trying edibles for the first time should start with a low dose and wait at least 2 hours before taking more. For safety, remember the saying: “Start low, go slow!”

    Inhaling (Vapor or Smoke)

    Cannabis can be inhaled through vapor or smoke. Effects can be felt within seconds to minutes and can last 2 to 3 hours.

    Safety Notes:

    • Many cannabis products contain mold. Because vaping cannabis uses lower heat than smoking, it may not kill mold as effectively as smoking.
    • Smoking (burning cannabis) exposes you to more toxins than vaping.

    Placing It on Skin (Topical)

    Cannabis creams, ointments, or patches can be applied to the skin. More studies are needed to understand how well and how quickly these work.

    Other Methods

    Some methods are intended to get cannabis straight into the bloodstream. These include placing it under the tongue, on the inner cheek, or inserting it into the rectum or vagina. To date, there is little research on how well these methods work in people with cancer.

    Potential Side Effects of Cannabis

    Like any medicine, the risks of taking cannabis depend on the type and amount of taken. If you experience any of the following side effects, talk with your care provider.

    Common Side Effects

    • Cough or throat irritation
    • Dizziness
    • Dry mouth
    • Headache
    • Mild confusion or memory problems
    • Mood changes, including anxiety
    • Nausea
    • Sleepiness

    Serious Side Effects

    • Changes in blood pressure
    • Paranoia or psychosis (breaks from reality)
    • Poor coordination
    • Rapid heart rate
    • Severe confusion

    Note: Taking too much cannabis does not stop your breathing, which can happen after taking too much prescription pain medicine.

    Other Risks

    • Driving: It is unsafe and illegal to drive under the influence of cannabis. Mixing cannabis with alcohol makes driving even more dangerous. Do not drive or operate heavy machinery while feeling the effects of cannabis.3
    • Children and pets: Store cannabis in a locked, safe place to prevent accidental ingestion by kids or animals.
    • Falls in older adults: Start with low doses and watch for confusion or unsteadiness.
    • Liver toxicity: Taking 300 mg or more of CBD by mouth daily may raise liver enzymes. These changes usually improve after stopping CBD.
    • Dependence: Long-term use can lead to dependence. Stopping regular cannabis use may cause withdrawal symptoms like anger, trouble sleeping, or changes in hunger.

    Frequently Asked Questions

      Does cannabis interact with other medicines?

      Yes. Cannabis can change how your body responds to some medicines. It can increase side effects or make medicines less effective. For example, cannabis can make you more sleepy if you also take certain pain medicines. It can also make it harder to think clearly, which could affect how you follow your treatment plan. Discuss cannabis with your care team before taking it.

      Can pharmacies provide cannabinoid medicines to help with side effects of cancer treatment?

      THC can be produced in a lab. Dronabinol and nabilone are FDA-approved forms of THC for medical use. Talk with your oncologist to learn more.

      Is cannabis legal for people with cancer in the U.S.?

      Cannabis is illegal under federal law. However, many U.S. states, including Massachusetts and New Hampshire, have legalized medical cannabis for cancer and other health conditions. Some states also allow non-medical use.

      Under federal law, CBD from hemp (cannabis with low THC levels) is legal. Check your state and local laws to see what is permitted where you live.

      How do people get medical cannabis?

      Dana-Farber does not dispense medical cannabis, but some medical providers may help you with the certification process. To buy medical cannabis, most states require a signed statement from a certifying clinician and a state registration card.

      • In Massachusetts, adults 18 and older can legally buy or grow small amounts of cannabis. Dispensaries sell cannabis for medical and non-medical use.
      • In New Hampshire, dispensaries sell cannabis for medical use only.

      For additional patient-friendly questions and answers, see: Cannabis and Cannabinoids in Adults With Cancer: ASCO Guideline Q&A.

      Other Symptom Support Options

      Dana-Farber offers many services to help manage symptoms and support your well-being:

      For more information, call Supportive Oncology at 617-632-6464.

      References

      *Dana-Farber lead researcher’s name appears in bold. 

      1Braun IM, Bohlke K, Abrams DI, Anderson H, Balneaves LG, Bar-Sela G, Bowles DW, Chai PR, Damani A, Gupta A, Hallmeyer S, Subbiah IM, Twelves C, Wallace MS, Roeland EJ. Cannabis and Cannabinoids in Adults With Cancer: ASCO Guideline. J Clin Oncol. 2024 May 1;42(13):1575-1593. doi: 10.1200/JCO.23.02596.

      2Cannabis and Driving, National Center for Injury Prevention and Control, https://www.cdc.gov/cannabis/health-effects/driving.html.  

      3Do EK, Ksinan AJ, Kim SJ, Del Fabbro EG, Fuemmeler BF. Cannabis use among cancer survivors in the United States: Analysis of a nationally representative sample. Cancer. 2021 Nov 1;127(21):4040-4049. doi: 10.1002/cncr.33794.