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.

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.