By Colleen Doherty, MD Medically reviewed by Arno Kroner, DAOM, LAc

Cannabidiol (CBD) is one of many compounds (called cannabinoids) found in the marijuana plant Cannabis sativa. CBD is known for its relaxing and pain-soothing effects.

CBD is non-psychoactive, so it does not give you the classic mind-altering euphoria or “high” felt from using marijuana—that effect comes from the cannabinoid called THC (tetrahydrocannabinol).

While the research is still very early, experts speculate that CBD may play a role in treating cancer, specifically by slowing tumor growth and inducing the death of cancer cells. CBD may also help manage unpleasant symptoms related to cancer and chemotherapy, such as pain, nausea, and vomiting.

CBD and Treating Cancer

There are a number of studies supporting CBD’s potential anti-cancer role—however, the majority are limited to in vitro and animal studies. For example, in various studies, there is evidence that CBD decreases the growth of lung and prostate tumors, provokes the cell death of colon, lung, and brain cancer cells, and reduces the spread (metastasis) of breast cancer.¹

While promising, large human clinical trials are needed to better understand whether CBD is truly effective in helping to treat cancer. Clinical trials would also allow experts to tease out issues like dosage, interaction with other cancer drugs, and CBD’s safety profile.

As of now, there are only a handful of human studies that have examined CBD’s anti-cancer role.

Here are a few examples:

• In one study of 119 cancer patients (most of the cancers were metastatic and traditional cancer therapies had been exhausted), CBD oil was given on a three day on and three days off schedule.² In most of the patients, an improvement in their cancer was noted, such as a decrease in tumor size. No side effects from CBD were reported.
• In a case study, an elderly man with lung cancer refused traditional chemotherapy and radiation for his cancer treatment and instead, self-administered CBD oil.³ After one month of taking the CBD oil, a computed tomography (CT) scan revealed near-total resolution of his lung tumor along with a reduction in the number and size of chest lymph nodes.
• In another study, two patients with aggressive gliomas (a type of brain tumor) were given CBD capsules in addition to chemoradiation and a multidrug regimen.⁴ Both patients had a positive response to the treatment with no evidence of disease worsening for at least two years.

Keep in mind—these studies are extremely small and lack a control group, so no finite conclusions can be drawn from them. Nevertheless, they spark further interest in the possible role of CBD in treating cancer.

CBD and Treating Cancer-Related Symptoms

There is scientific evidence, although limited and not robust, that CBD, THC, or a combination of the two, may be effective in alleviating certain cancer-related symptoms, such as pain, appetite loss, and chemotherapy-induced nausea and vomiting.

For instance, the drugs Marinol (dronabinol) and Cesamet (nabilone), which are synthetic forms of THC, are approved in the United States for treating chemotherapy-induced nausea and vomiting. Research suggests that dronabinol may also improve the taste of food, appetite, sleep, and quality of life in cancer patients.⁵Marinol: A Good Alternative to Medicinal Marijuana?

In addition, a mouth spray that contains both THC and CBD (called Sativex) is being investigated for its role in treating cancer pain (especially nerve-related pain) that is poorly controlled by opioids.⁶ The drug is currently not available in the United States, but it is available in Canada for treating advanced cancer pain.

Lastly, research has found that in the general population (so not necessarily patients with cancer), CBD can reduce anxiety and improve sleep quality.⁷ This finding is helpful, considering the diagnosis and treatment of cancer is often overwhelming and wrought with fear and worry.

CBD Considerations

With the potentially emerging use of CBD in treating cancer and/or its related symptoms, there are a few issues to consider.

Formulations

CBD oil is perhaps the most commonly utilized formulation of CBD, as it’s easy to use and allows for a high dose of consumption. However, CBD comes in many other forms—gummies, tinctures, capsules, vapes, and ointments, to name a few.

Sorting out how to best administer CBD to patients with cancer may prove to be challenging, as various formulations may work or absorb differently.

Side Effects

While research suggests that CBD is generally well-tolerated, we need to more closely examine potential side effects in patients with cancer. In addition, we still do not know the long-term effects of taking CBD, or how it interacts with other medications.

Short-term side effects of CBD may include:⁸

• Reduced or increased appetite
• Weight gain or loss
• Tiredness
• Diarrhea
• Increase in liver enzymes

If CBD is combined with THC (in the form of medical marijuana), other side effects may occur, such as:⁹

• Dizziness
• Dry mouth
• Nausea
• Disorientation and confusion
• Loss of balance
• Hallucinations

Legal

While CBD by itself is federally legal (as long as the product is derived from hemp and contains no more than 0.3% THC), marijuana is not (although, it is legal in some states).

CBD is only available by prescription in the United States in the form of a drug called Epidiolex. This drug is used to treat refractory epilepsy.

Due to these legal conundrums, CBD products may not be as tightly regulated as hoped. With that, products that claim they have a certain CBD dosage may actually contain a different amount or even contain traces of THC. This is why it is important to only take CBD under the guidance of your personal physician.

A Word From Verywell

The prospect of incorporating CBD into cancer care is intriguing but still requires much more investigation. Until then, if you are considering trying CBD (whether you have cancer or not), it’s best to talk out the pros and cons with your doctor.