Marijuana & Breast Cancer: Studies Patients Should Know

Marijuana Breast Cancer Studies
Medical marijuana is increasingly recognized for its potential in alleviating cancer symptoms and treatment-related side effects. Recent studies suggest that cannabinoids, the active compounds in marijuana, may have the ability to kill tumor cells without affecting non-transformed cells. In a survey, 70% of breast cancer patients believed the benefits of cannabis outweighed the risks, and they reported using it to manage symptoms such as pain, insomnia, anxiety, stress, and nausea/vomiting. However, it's important to note that while these findings are promising, medical marijuana is not currently an FDA-approved cancer treatment, and research is ongoing.
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Physicians and patients alike have long acknowledged marijuana’s ability to ease cancer symptoms and treatment-related side effects. But the idea that cannabis – once described by the U.S. Attorney General as only “slightly less awful than heroin” – can actually fight the disease itself? Well, that’s the kind of crazy talk that could get you laughed off the Internet.

Until now.

When one scientist publishes a study, it starts a conversation. When a second researcher chimes in, it attracts some attention. But when the biggest names in peer-reviewed literature – ranging from Molecular Cancer to The British Journal of Pharmacology – routinely highlight advances in a particular area of research, you start to wonder:

Did the mainstream media – and along with it: prominent politicians and healthcare officials – get it all wrong?

According to some of the world’s most respected scientists, the answer is YES.

Why Don’t Doctors Talk About Cannabis?

In a new survey that’s grabbed headlines, researchers questioned over 600 breast cancer patients, finding that – while 70% believed that the benefits of cannabis outweighed the risks – less than 4% of the 306 patients who said they wanted more information ranked their physician as the “single most helpful source of information.” In fact, most patients ranked websites and friends and family as more informative!

Making matters worse, while 39% of participants discussed cannabis with their physicians, over 75% of those discussions were patient-initiated. But instead of focusing on the failures of the healthcare system (with so much available research and legalized medical cannabis in over 70% of U.S. states, why weren’t doctors initiating these conversations?), the media was quick to point the blame at patients, with headlines such as Many People Being Treated for Breast Cancer Use Cannabis But Don’t Tell Their Doctor and Breast Cancer Patients Turning to Marijuana – But Many Hide It from Doctors.

So why the blame game? And why the hesitancy on the part of mainstream (i.e., non-cannabis) physicians to 1) familiarize themselves with cannabis research, and 2) objectively communicate this information with patients?

While both questions are complex, their answers share a common ground rooted in stigma and outdated reporting. For an example, we need look no further than, which states: “It’s important to know that cannabis is not a cure or treatment for cancer itself, even though there are many such claims online.” As peer-reviewed studies have repeatedly confirmed marijuana’s ability to (you guessed it!) treat the disease itself, a more accurate statement might be phrased as: “Cannabis is not a cure or FDA-approved treatment for cancer itself…”.

While a seemingly insignificant change, this small distinction makes all the difference. Because, while the merits of medical cannabis may not be recognized by the healthcare system at large – as evidenced by Cancer‘s recent survey – its tumor-fighting potential is irrefutable.

Below, we take a closer look at the cannabis studies that physicians and the press aren’t discussing with breast cancer patients.

How Does Marijuana Help Cancer Symptoms?

Before diving into cancer-fighting studies, it’s important to recognize marijuana’s long-held role in treating a variety of disease-related symptoms. For instance, in the survey above, participants reported that they used cannabis for the following symptoms:

  • Pain: 78%
  • Insomnia: 70%
  • Anxiety: 57%
  • Stress: 51%
  • Nausea/Vomiting: 46%


Importantly, 75% reported that marijuana was “extremely or very” helpful at relieving their symptoms, while 57% said that they had found no other way of treating their symptoms.

These findings echo earlier studies confirming marijuana’s efficacy in addressing each symptom:

* Pain: According to the Journal of Clinical Pharmacology, a study of advanced cancer patients revealed a correlation between higher doses of THC and increased pain relief. For more information, see: Marijuana & Cancer Pain and Pain Relief: Marijuana vs. Opioids.

* Insomnia: Studies have shown that marijuana can shorten the time it takes to fall asleepdecrease rapid eye movement (REM) sleep, and increase deep, slow-wave sleep. For more information, see: Insomnia Study: Marijuana Increases Slow-Wave Sleep.

* Anxiety: A 2019 peer-reviewed study found that after completing an average two-month prescription course of medical marijuana, 30.1% of patients had discontinued benzodiazepines (e.g., Xanax, Ativan, Valium). At a follow-up after two prescriptions, 65 total patients (44.5%) had discontinued benzodiazepines. For more information, see: Anxiety & Marijuana: What Science Says.

* Nausea/Vomiting: As reported by the British Journal of Pharmacology, “considerable evidence demonstrates that manipulation of the endocannabinoid system regulates nausea and vomiting in humans and other animals.” For more information, see: How Medical Marijuana Helps Nausea.

However, while marijuana’s ability to treat cancer symptoms is valuable, it’s the plant’s potential to fight cancer itself that’s at the heart of today’s review.

Can Cannabis Kill Cancer Cells?

Perhaps more succinctly than any other source, the National Cancer Institute confirms the claim that marijuana can, in fact, kill cancer cells:

Cannabinoids appear to kill tumor cells but do not affect their non-transformed counterparts and may even protect them from cell death.

This statement appears as a summary of previous research establishing the same point. For instance, a 2012 study published by the Journal of Molecular Medicine found that CBD increased endocannabinoid levels and reduced cell proliferation in mice with colon cancer. Likewise, an earlier study featured by Molecular Cancer Therapeutics showed that CBD “induced programmed cell death in breast cancer cells.”

This second finding, featured by Molecular Cancer Therapeutics, garnered significant press at publication; although, oddly, similar findings are largely absent from current, mainstream coverage of marijuana. Regardless, the study – titled Cannabidiol Induces Programmed Cell Death in Breast Cancer Cells by Coordinating the Cross-Talk Between Apoptosis and Autophagy – serves as a landmark in medical cannabis research.

As its study authors write:

[W]e showed that CBD, a plant-derived cannabinoid, preferentially kills breast cancer cells by inducing ER stress, inhibiting mTOR signaling, enhancing ROS generation, and mediating a complex balance between autophagy and mitochondria-mediated apoptosis in MDA-MB-231 breast cancer cells. These findings support the continued exploration of CBD as an alternative agent for breast cancer treatment.

Supporting this finding, Cancer Medicine notes:

[The] main effect of cannabinoids in a tumor is the inhibition of cancer cells’ proliferation and induction of cancer cell death by apoptosis.

As the Journal of the National Cancer Institute noted back in 1975 (after demonstrating that mice with cancer showed prolonged survival rates following THC treatment):

That [cannabis] compounds readily cross the blood-brain barrier and do not possess many of the toxic manifestations of presently used cytotoxic agents, makes them an appealing group of drugs to study.

Medical Marijuana & Breast Cancer Studies

While arguablly the most famous marijuana and breast cancer study to date, the Molecular Cancer Therapeutics article (detailing how CBD “induced programmed cell death in breast cancer cells”) is not the only piece of research on the subject.

As the National Cancer Institute summarizes:

Other studies have also shown the anti-tumor effect of cannabinoids (i.e., CBD and THC) in preclinical models of breast cancer.

For instance, Molecular Cancer reports:

[Our] results provide a strong preclinical evidence for the use of cannabinoid-based therapies for the management of ErbB2-positive breast cancer.

Elaborating, the study authors explain:

The antitumoral potential of cannabinoids has been documented both in vitro and in animal models of cancer. These compounds inhibit breast cancer cell proliferation in vitro through processes that include cell cycle arrest, hormone and growth-factor receptor modulation, and apoptosis induction.

[…] Remarkably, this is, to the best of our knowledge, the first report supporting that cannabinoids hamper not only tumor growth but also tumor generation.

Adding to this literature, researchers with Breast Cancer Resistant Treatment write:

Using immune competent mice, we then show that treatment with CBD significantly reduces primary tumor mass as well as the size and number of lung metastatic foci in two models of metastasis. Our data demonstrate the efficacy of CBD in pre-clinical models of breast cancer.

In conclusion, the study authors note:

Since CBD has a low toxicity, it would be an ideal candidate for use in combination treatments with additional drugs already used in the clinic. Importantly, CBD appears to be interacting through a cellular system that regulates the expression of key transcriptional factors (e.g., Id-1) that control breast cancer cell proliferation, migration, and invasion.

The experiments described in this manuscript not only define the pathways that CBD is working through to control breast cancer cell aggressiveness, but also demonstrate the efficacy of CBD in pre-clinical models. A greater understanding of this system may lead to future therapies for breast cancer patients.

Important Notes

While today’s review highlights significant (and growing!) literature supporting marijuana’s use in fighting breast cancer, it’s important to note that research is still developing and that medical marijuana is not, at this time, an FDA-approved cancer treatment. The information presented today is intended for educational purposes only.

Updated: March 5, 2024

Jessica Walters

Jessica Walters serves as CannaMD's Chief Medical Researcher. Prior to her time at CannaMD, Jessica earned her degree from Harvard where she focused on neuropsychology. Her personal research interests include psychosocial interventions for obesity, depression, and generalized anxiety disorders.


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