What is Cannabidiol (CBD)? Common Questions Answered

By Benjamin S. Kematick, PharmD, BCACP
A clinical pharmacy specialist in Dana-Farber’s Division of Palliative Care

CBD is a phytocannabinoid, a naturally occurring compound found in the flower of cannabis species. CBD is different from the better-known phytocannabinoid delta-9-tetrahydrocannabinol (THC) in that it does not produce an intoxicating effect.

Like CBD, THC is found in both marijuana and hemp, but the trace amount in hemp is so negligible it renders the plant non-psychoactive. Both CBD and THC activate the body’s endocannabinoid system—a network of receptors in the human body that control mood, pain sensation and other life functions.

A significant proportion of what is classified as “medical marijuana” refers to whole-plant marijuana, or an unprocessed plant comprised of many active chemical compounds, including CBD and THC, that work together to produce synergistic effects. In contrast, pharmaceutical cannabinoids are created in a lab using the plant’s isolated chemical compounds. To date, the U.S. Food and Drug Administration (FDA) has not recognized or approved the whole marijuana plant as medicine, due in large part to a lack of quality research to properly assess its risks and benefits.

In 2014, research related to industrial hemp, specifically—which is defined as cannabis sativa plants containing less than 0.3% THC—became legal at the federal level. This research exemption has led to greater availability of hemp-derived CBD products on the market, both online and in stores.  So, while cannabis-related laws vary by state, there is now increased awareness of CBD and its potential health benefits, as well as greater availability of CBD products.

CBD oil.
CBD oil.

In medicine and the oncology space specifically, why are CBD and medical marijuana controversial? Is there any evidence that CBD can cure cancer?

From a broad medical standpoint, much of the controversy surrounding the use of cannabis and its compounds today relates to its increased availability to a growing base of interested consumers despite massive gaps in clinical research to understand how these compounds affect people. Since 1970 and the passing of the Controlled Substances Act, there has been little high-quality, consistent medical research about cannabis and its various ingredients—including potential benefits and risks. Many claims made today about purported benefits tend to minimize the potentially harmful effects of marijuana. More medical research is needed to fully understand risks and benefits.

Another claim suggests that marijuana and CBD have profound cancer-inhibiting qualities, such as the ability to shrink or stop tumor growth. However, there has been scarce controlled scientific research into the antitumoral effect of cannabis in humans, and much of the current data is pre-clinical. One study examined the effect of intratumorally-administered THC on recurrent gliomas, but it found no impact on survival.

Also controversial is the variety of medical marijuana products available, all with different proportions of more than 60 potentially-active phytocannabinoids. These products include capsules, gummies, chocolates, and other edible products, along with tinctures, oils, and flowers. Each preparation has slightly different characteristics, which is likely to affect the product’s final therapeutic effect. Much of the available evidence in support of the use of whole plant medical marijuana involves the inhaled routes, by way of flowers or vaporized oils. Without more rigorous testing of these various dosage forms, health care professionals have little more than guesses or anecdotal evidence about how a particular product will affect most patients.

What are some of the reported health benefits of CBD—broadly, and for cancer patients?

Cannabidiol oral solution is now FDA-approved for the treatment of rare epileptic disorders that have been historically difficult to treat. The clinical trials that led to this FDA approval have also informed researchers of the side effects, drug interactions, and other critical properties of CBD when ingested orally.

There is evidence to suggest CBD may have some benefit for those with social anxiety disorder, sleep disorders, and chronic pain—issues that affect, among others, patients undergoing cancer treatment. Preclinical evidence has shown CBD may be useful in treating substance-use disorders, neurodegenerative disorders, and inflammation, as well.

CBD can also antagonize the intoxicating effects of THC, which can make medical marijuana more tolerable to many patients who find the THC-intoxication to be too unpleasant for them to continue to use for relief for symptoms like chemotherapy-induced nausea.

Are there any potential side effects associated with CBD?

While recognizing the need for additional research, CBD consumed orally has shown to be mostly well tolerated. In the trials for the approval of liquid oral cannabidiol the most common side effects included decreased appetite, diarrhea, somnolence (drowsiness), fatigue, insomnia, infection, and rash. Patients treated with cannabidiol were also noted to have an increase in liver enzymes, so those with liver complications should be cautious about trying CBD.

If a patient wants to try CBD products for cancer-related symptom relief, what are their options?

Laws regarding the sale of medical marijuana and related products vary by state, but in states where it is legal, cancer is a qualifying condition. If a patient residing in a legal state wants to try CBD products, it is recommended that they talk to their oncologist or cancer care team about obtaining certification as a medical marijuana patient to shop at a local dispensary. Medical marijuana patients do not pay the same taxes as adult recreational users, and dispensaries for medical and recreational use are required to reserve a portion of inventory for medical patients. It is more complicated, and therefore not recommended, to purchase CBD products available online, as those products do not undergo the same level of scrutiny as that of products under the purview of state regulatory systems.

Where do you hope to see CBD research headed in the next few years?

As the national regulatory landscape continues to shift, many patients and clinicians hope for more research on the effect cannabis and CBD may have in treating distressing cancer-related symptoms, including pain, anxiety, insomnia, and nausea, among others. There is also much to learn about the endocannabinoid system and the variety of roles it may perform in the body, including its role in cancer proliferation.

While limited preclinical evidence has demonstrated a potential anti-tumor effect of cannabinoids, there is no high-quality medical evidence proving marijuana’s efficacy and safety. This is another area where more research, based on this preclinical evidence, is needed.

13 thoughts on “What is Cannabidiol (CBD)? Common Questions Answered”

  1. Hello. Thank you for your information. I have Stage IV ovarian cancer and have the approval from my oncologist to use medical marijuana. My husband, who is a retired pharmacist, makes suppositories for me to use every night. Right now we are up to 500 mg of high THC Rick Simpson type cannabis oil in each suppository. ( John makes the RSO) I have had no side effects at all using it this way. I am also considering a vaginal suppository. I don’t know if I will avoid the psychotic effects using the cannabis vaginally. I will start with a very small dose and see.
    Do you have any clinical experience with either vaginal or rectal suppositories?
    Thank you.

    • Hi Rose,

      Thank you for reading. Unfortunately, we cannot provide medical advice online. We would recommend you reach out directly to a medical professional to discuss this.


  2. We need much more information including toxins in production from herbicide to fertilizers and soil quality. Consistency in product, and real benefits v risks…imo

  3. I am very interested in this. I am a patient of Ursula Matulonis. I will be checking with her about this when I see her Dec 24th

  4. i have been taking CBD for about 3 months now. it helps me with the adverse effects of my monthly abdominal injections for stage 4 prostate cancer which are in and of themselves painful to endure. i use cbd just after my injections and when i have a hormonal hot flashes. kudos to the cancer treatment community. i would like to personally thank John Moores Center at UCSD, City of Hope and soon the Dana Farber center at Harvard where i would like to enroll in a clinical trial having to do with mRNA and chromatin remodelling.

    James Kahelin
    San Diego, California

    • Hi Judith,

      A response from the post’s author, Benjamin S. Kematick, PharmD, BCACP: “There are no high quality studies suggesting efficacy for CBD or cannabinoids in fibromyalgia that I am aware of. Anecdotally patients say it is helpful. https://www.ncbi.nlm.nih.gov/pubmed/27428009

      CBD and other cannabinoids in preclinical studies have been reported to reduce inflammation. This is thought to be via the effect of the endocannabinoid system on known inflammatory pathways. It is important to recognize that the anti-inflammatory effect has been mostly studied in non human mammals. This is an area where more research is needed. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2828614/

      Wishing you all the best,

  5. I use CBD and medical marijuana to control the inflammation and pain caused by chemo induced peripheral neuropathy, PTSD and anxiety. I use a combination of oil, edibles and creams.

    Work with a reputable independent dispensary to get delivery and dosage methods that work for you.

  6. Are there any current research programs in place to test some of these claims? I use CBD in tincture form for pain relief at the moment. It is more effective than Tylenol for sure. Probably at the same pain relief level of Oxycodone, but without the addictive risks.

  7. I have been using a CBD salve with Lidocaine for pain from a total knee replacement. It seems to work much better than drugstore rub-on products with Lidocaine. It is expensive, or I would slather it all over my arthritic body.

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