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Can cannabis and CBD cure cancer? The current state of science

Franjo Grotenhermen

It has long been known that THC and cannabis can help people with cancer better manage the disease.

Cannabis products can help with nausea and vomiting, stimulate appetite, relieve pain, improve sleep and brighten mood. This is described in the scientific literature and reported by many of my patients.

The reliability of the effect depends very much on the symptom. Pain is relieved in only a smaller proportion of patients. Appetite, however, is often well stimulated.

Much depends, of course, on whether the preparation taken is also well tolerated. CBD, on the other hand, has no appetite-enhancing effects and is not effective against nausea. However, a study on animals has shown that small doses of THC and CBD together could help against nausea. CBD mostly does not work against pain, but it can relieve anxiety and improve mood and sleep in some people. Sometimes, however, it can worsen sleep.

The effect on cancer

However, when it comes to the effect on cancer itself, it wasn't long ago that the discussion focused on whether cannabis causes cancer. There was evidence that smoking cannabis could slightly increase the development of lung cancer, testicular cancer, and head and neck cancer. In recent years, however, the focus has changed. Today, the question is mainly: can cannabis, THC and CBD cure cancer or contribute something to cure? This is largely based on results of basic research with cells various cancers and animals, as well as an increasing number of case reports of individuals who had taken either highly concentrated extracts with THC and/or CBD on their own or under a doctor's guidance.

What is cancer?

Cancer is a broadly used term for diseases in which cells can divide without control and generally invade other tissues. Cancer is not just one disease, but many diseases: More than 100 different types of cancer are described by the World Health Organization in terms of their fine-tissue characteristics, and there are probably hundreds, if not thousands, of cancers when considered in terms of their molecular and genetic profiles. In Germany, approximately 500,000 people develop cancer each year.

Epidemiological studies

Epidemiology is concerned with the distribution as well as the causes and consequences of diseases and symptoms in the population. This distinguishes epidemiological studies from clinical trials, in which a group of patients is exposed to specific treatments. In 2005, various institutions in the USA from the University of California and the University of Utah, in collaboration with the International Agency for Research on Cancer (IARC) of the World Health Organization, had summarized the epidemiological data to date on the relationship between cannabis smoking and cancer. There were some slightly increased and some slightly decreased cancer risks from smoking cannabis. The authors concluded that no conclusive assessment is possible so far and call for further methodologically sound studies on the association between cannabis smoking and cancer. Although cannabis smoke qualitatively contains the same combustion products as tobacco smoke, except for nicotine in tobacco and cannabinoids in cannabis, it was noticed in the largest epidemiological study that cannabis smokers had a statistically non-significant decreased risk of lung cancer by about 20-30%, while tobacco smoking was associated with a significant increase in risk. The authors suggested that the cancer-causing constituents of smoke (nitrosamines, benzpyrene, etc.) may roughly balance those of the cancer-inhibiting constituents in cannabis (THC and other cannabinoids) in terms of their effects.

How do cannabinoids inhibit cancer growth?

Since the late 1990s, a number of mechanisms have been discovered by which various cannabinoids inhibit the growth of or kill cancer cells (Abrams & Guzman 2020).

These include the following mechanisms:

  1. The induction of cancer cell death through so-called apoptosis (programmed cell death),

  2. the inhibition of cancer cell proliferation,

  3. the inhibition of the formation of new blood vessels in the tumor,

  4. inhibition of the formation of metastases (daughter tumors), among other things by inhibiting the ability of cancer cells to migrate.

Other effects have been described in some studies, including effects on the immune system that resulted in immune cells better recognizing cancer cells, or prevention of cancer cell chemoresistance by cannabinoids. Chemoresistance is similar to the development of resistance to antibiotics in bacteria. Cancer cells can also develop resistance to certain chemotherapeutic agents, so that they initially work successfully for a few months, and then the effect wears off. Interestingly, cannabinoids induce programmed cell death of cancer cells without affecting the viability of non-malignant healthy cells. This distinguishes cannabinoids from other chemotherapeutic agents, which can also damage healthy cells, with all the negative effects (hair loss, blood count changes, damage to mucous membranes, etc.).

Interaction with other cancer therapies

In some studies, the combined administration of cannabinoids with cancer drugs or radiation has been shown to enhance each other. For example, researchers demonstrated in rats that both CBD and THC were effective against glioblastomas, very aggressive brain tumors. When these two cannabinoids were combined with the standard chemotherapeutic agent temozolomide, the therapeutic effects were stronger than those of any of the three substances alone. Cannabinoids also enhanced the efficacy of radiotherapy for glioblastoma. Some other chemotherapeutic agents were also found to be enhanced by the concomitant administration of cannabinoids. A well-known example is the mutual enhancement of the chemotherapeutic drug doxorubicin and CBD in breast cancer.

A case report involving THC-rich cannabis extracts.

In 2014, Canadian researchers published in the journal Case Reports in Oncology the case of a 14-year-old girl who suffered from a very aggressive form of acute lymphoblastic leukemia (Singh & Bali 2013). Bone marrow transplantation, aggressive chemotherapy and radiation therapy were performed. The treatment was stopped after 34 months because the girl could not be helped any further. With no other possible solutions available through conventional therapeutic approaches other than end-of-life care, the family administered oral cannabis extracts to the patient, which were primarily rich in THC. Leukemia has the advantage of being easy to track the development of the number of cancer cells in the blood. In the first weeks of treatment, the number of leukemia cells (lymphoblasts) was still increasing because the dose of cannabinoid administered was still too low to induce apoptosis in the cancer cells. Then, however, after 39 days of therapy, the number of cancer cells in the blood dropped from 374,000 per milliliter to less than 1000 per milliliter within a few days.

Some case reports with CBD

in October 2019, physicians at Klagenfurt Hospital in Austria published a case series of patients with grade IV glioblastoma who had received CBD in addition to their standard therapy (Likar et al 2019). They indicate that this tumor is associated with a median survival of approximately 14 to 16 months. Maximal surgical resection followed by radiotherapy and chemotherapy has been the mainstay of treatment for many years, although survival can only be extended by a few months. In their paper the journal Anticancer Research, a total of nine consecutive patients with this malignant brain tumor were described as a case series. All patients received CBD at a daily dose of 400 mg (2 × 200 mg) concurrently with the standard treatment regimen of maximal surgical resection followed by radiochemotherapy. At the time of article submission, all but one patient was still alive with a median survival of 22.3 months (range: 7 to 47 months). Commenting on this, the authors write, "This is longer than expected."

A clinical trial

For the first time, results of a controlled clinical trial were published in 2017 showing that cannabis could inhibit cancer growth and improve survival not only in animal studies but also in humans (Twelves et al 2017). This study involved 21 patients with recurrent glioblastoma. 12 patients received the standard chemotherapy drug temozolomide plus a cannabis extract containing THC and CBD in approximately equal amounts, and 9 patients received the standard therapy of temozolomide plus placebo. After 1 year, 53% of patients who received temozolomide plus the placebo alone were still alive, while the 1-year survival rate in the cannabis group was 83%. This difference was statistically significant. It suggests that the addition of cannabinoids may improve the therapeutic outcome of standard therapies.

Testing for cannabinoid receptors

The brain has a particularly high density of cannabinoid receptors, so it is not surprising that various brain cancers in particular might respond well to cannabinoids. However, cannabinoid receptors are distributed throughout the organism. In the future, it may be useful to screen cancer cells for the presence of cannabinoid receptors to obtain clues as to whether cannabinoids could be used therapeutically in these cases.

Summary and Conclusion

In summary, it is desirable that further clinical studies be conducted to better understand the potential of cannabinoids in cancer treatment. Until then, many years will pass, because clinical research is always laborious and lengthy. In the meantime, we will have to live with uncertainty regarding this issue. We will continue to read and hear about cures of individual cancer patients by cannabis products. It is equally irresponsible for individuals - Rick Simpson is well known - to advocate foregoing normal cancer treatment, which often leads to a cure, in favor of the use of cannabis products and, on the other hand, inaccurate to completely deny the treatment with cannabis or THC and CBD a possible additional benefit in cancer therapy.


  • Abrams DI, Guzmán M. Can Cannabis Cure Cancer? JAMA Oncol,16. Januar 2020 [im Druck] Grotenhermen F. Cannabis bei Krebs: mehr Chancen als Risiken? DZO (Deutsche Zeitschrift für Onkologie), 2018;50(4):188-192. Online frei verfügbar.

  • Grotenhermen F. Cannabis gegen Krebs: Der Stand der Wissenschaft und praktische Folgerungen für die Therapie. Solothurn, Schweiz: Nachtschatten Verlag, 2017.

  • Likar R, Koestenberger M, Stultschnig M, Nahler G. Concomitant Treatment of Malignant Brain Tumours With CBD - A Case Series and Review of the Literature. Anticancer Res. 2019;39(10):5797-5801.

  • Singh Y, Bali C. Cannabis Extract Treatment for Terminal Acute Lymphoblastic Leukemia with a Philadelphia Chromosome Mutation. Case Rep Oncol 2013;6:585-592

  • Twelves C, Short S, Wright S. A two part safety and exploratory efficacy randomised double-blind, placebo controlled study of a 1:1 ratio of the cannabinoids cannabidiol and delta-9-tetrahydrocannabinol (THC:CBD) plus dose-intense temozolomide in patients with recurrent glioblastoma multiforme (GBM). J Clin Oncol 2017;35(15 suppl): 2046.