Cannabis and Cancer

Cannabis and Cancer

Introduction to Cannabis

This plant is most commonly known as marijuana, its scientific name is Cannabis Sativa. Cannabis contains compounds called cannabinoids, and two of these cannabinoids are being used medicinally. One is cannabidiol (aka CBD), which has become wildly popular for insomnia, pain, and anxiety. Another is THC, or tetrahydrocannabinol, which is the intoxicating component of Cannabis.

How Does Cannabis Work?

The cannabinoids in Cannabis mimic our body’s endocannabinoids, or “internal” cannabinoids, to produce their effects on us. Like many plant-derived medicines, cannabinoids can now be made synthetically in a lab.

CBD and THC can be used together or separately and this would depend on the purpose of use. They are either taken orally, for example CBD enriched hemp oil, or taken by inhalation, vaping THC or smoking the plant. Synthetic THC pharmaceuticals are called dronabinol and nabilone, are available as capsules or liquid.

We don’t yet know what the other compounds present in Cannabis, such as other cannabinoids (over 100), terpenes, and flavonoids, do in our bodies. It may turn out that the whole plant works better than its’ individual parts.

Can Cannabis Control Side Effects of Cancer and Cancer Treatment?

Cannabis may help with nausea, vomiting, low appetite, pain, neuropathy, cognitive impairments and sleep.
  • Nausea and vomiting due to chemotherapy – pharmaceuticals used for this problem are very effective to stop vomiting; but patients may still have residual nausea. THC can help control this nausea and it is important to take an inhaled form of Cannabis in this scenario.
  • Low appetite – THC helps to increase appetite, resulting in better ability to maintain weight.
  • Pain – Cannabis is known to be beneficial for pain and can be used alongside opiates. Opiates have more detrimental side effects than Cannabis and more addictive potential. Cannabis use helps patients need less opiate medication.
  • Neuropathy – no studies about Cannabis with chemotherapy induced neuropathy are available yet. But there are studies with other medical conditions causing neuropathy that show benefit.
  • Cognitive symptoms – poor memory and brain fog are a big complaint of patients taking chemotherapy. Some research suggests that CBD may help; THC may make it worse.
  • Sleep – there is very little information on Cannabis and insomnia. Clinical observations suggest CBD is very helpful for sleep.

Does Cannabis Have a Part to Play in Treating Cancer?

Many people battling cancer ask about CBD/THC as potential natural anticancer medicine. There is growing evidence that cannabinoids may inhibit tumor growth and metastasis.

Current Lab Research: In lab and animal experiments, CBD can stop cancer cell growth in a wide variety of cancers. It also may reduce “chemo-resistance”, which describes what happens when cancer medicines are working to treat a cancer, then after being taken for a period of time the cancer begins to grow anyway. There are lab experiments that suggest CBD can decrease the possibility of chemo-resistance to the medicines used to treat glioblastoma, a brain cancer. THC in lab research appears to both promote and inhibit growth of breast cancer cells. So this area definitely needs more close study and clarification, as well as human trials to confirm the lab observations.

Current Human Research: After science has studied a compound in a lab and animals, it is given to human subjects in safety, dosing and effectiveness studies. There is very little human research available about Cannabis and anticancer effects. Studies with breast cancer patients and brain tumor patients suggested an increase in overall survival time and a decrease in circulating tumor cells, in patients that combined CBD/THC with cancer treatments.

Safety and Side Effects

CBD and THC do have some side effects. CBD can cause drowsiness, fatigue, irritability, and diarrhea. THC can cause brain fog, drowsiness, and euphoria (intoxication). Together they cause any of the listed side effects plus nausea or lowered blood pressure. Additionally, there is limited information on the long-term safety of CBD, especially related to brain and cognitive function.

In some of the research, THC appears to have a suppressive effect on the immune system. This raises the question about combining it with immunotherapy drugs, because theoretically it could cause people to have less response to these medicines. Immunotherapy drugs rely on your body’s immune system to do the work of killing cancer. And since we are always striving to keep your immune system healthy during cancer treatments, we need more information on the extent of this potential problem with THC.

Take Home Message

We can’t draw any conclusions about any of this yet, we simply don’t have enough information! Until recently, it has been difficult to study Cannabis for medical purposes, because of its’ legal and social status. For this reason, it has been very slow to reach human clinical studies. With many states now legalizing cannabis, it is finally able to be studied more easily in clinical trials. Currently, there are many trials being planned or recruiting patients with varying doses of CBD alone, CBD/THC together in certain ratios and with many different types of cancer.

It will be interesting and exciting to discover exactly how cannabinoids can be used to the maximum benefit of cancer patients. There may be synergy between current cancer drugs and cannabis, to slow cancer growth. And we will find out eventually which combination of cannabinoids are most effective in each clinical scenario. Until we know for sure, we continue to weigh the benefit vs. risk of using Cannabis for each patient as an individual.


1.      Cancers (Basel) 2020 Apr 23;12(4):1033. doi: 10.3390/cancers12041033. Can Hemp Help? Low-THC Cannabis and Non-THC Cannabinoids for the Treatment of Cancer. Farjana Afrin, Mengna Chi, Andrew L Eamens, Ryan J Duchatel, Alicia M Douglas, Jennifer Schneider, Craig Gedye, Ameha S Woldu, Matthew D Dun

2.      Mayo Clin Proc. n September 2019;94(9):1840-1851 n

3.      Annals of Palliative Medicine, Vol 6, Supplement 2 (December 2017): 1 A selective review of medical cannabis in cancer pain management. Alexia Blake, Bo Angela Wan, Leila Malek, Carlo DeAngelis, Patrick Diaz, Nicholas Lao, Edward Chow, Shannon O’Hearn

4. . 2019; Published online 2019 Aug 1. doi: 10.1177/1758835919866362 Opportunities for cannabis in supportive care in cancer, Amber S. KlecknerIan R. KlecknerCharles S. KamenMohamedtaki A. TejaniMichelle C. JanelsinsGary R. Morrow, and Luke J. Peppone

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