Despite the many wonders of modern medicine, cancer continues to plague humanity. As it stands, cancer claims around 600,000 lives each year in the United States, and remains the second leading cause of death across the world. Although often attributed to genetic factors, only 7% of cancers are hereditary. The remaining 93% stem from environmental causes such as diet, pollution, bacteria, and communicable diseases.
On top of cancer’s devastating death rate, conventional methods of treatment — chemotherapy, radiotherapy, and surgery — fail more than they succeed. Such a poor rate of remission and recovery fuels a search for new therapeutics, both technological and traditional.
Paradoxically, cannabis use may promote and inhibit cancer cell growth. Although numerous safer options exist — edibles, vaporization, and sublingual administration — many cannabis users still opt to smoke the herb.
Smoking, in general, does the body no favours. The smoking of cigarettes contributes to the majority of lung cancers. Smoking cannabis also produces carcinogens and other damaging substances. However, a recent review of the scientific literature suggests that smoking cannabis may actually reduce the risk of cancer.
The risk of smoking cannabis: A look at the data
A fascinating scoping review and meta-analysis published within the journal Cannabis and Cannabinoid Research set out with the intention of evaluating the correlation between smoking cannabis and cancer risk.
Before gathering the data and performing the analysis, the authors explored both the cancer-inducing and cancer-inhibiting effects of smoking cannabis. This method of consumption exposes the lungs to large quantities of tar and polycyclic aromatic hydrocarbons — perhaps more so than smoking tobacco.
Conversely, the cannabis plant serves as a complex source of phytochemicals. The resinous buds of this medicinal herb contain over 100 cannabinoids, 200 terpenes, and an assortment of flavonoids.
Not only do cannabinoids work alone to produce antioxidant and anti-inflammatory actions, but they also synergise with terpenes to create an entourage effect that potentially makes them more therapeutically sound.
These factors prompted the authors to draw up three separate hypotheses. First, they speculated that the carcinogenic effects of smoking cannabis would subject users to increased cancer risk. Secondly, they proposed the possibility of the carcinogenic and antitumor effects cancelling each other out. Finally, they suggested that the antitumour effects may dominate, therefore reducing cancer risk.
The authors analysed a collection of research papers that explored the association of smoking cannabis with a multitude of cancer types, including testicular, lung, bladder, oral, head, neck, and lymphoma.
After vetting studies for risk of bias, they selected a total of 29 high-quality papers. Following a series of statistical tests, the research team found that the data did not support the hypothesis that cannabis use increases cancer risk. In fact, they found a significant association between cannabis use and a decreased risk of the disease, with the exception of testicular cancer.
Overall, they found an estimated decreased risk of 10% in cannabis smokers. However, the authors state the possibility of an even higher percentage in reality.
Cancer and cannabis: Why might smoking reduce cancer risk?
Cannabis works to produce possible antitumor effects in the body in a very specific manner. Many cannabinoids interface with a regulatory network that keeps the body in a state of biological balance, or homeostasis. Known as the endocannabinoid system (ECS), parts of this network are found all throughout the body, from the immune system and nervous system to the skin.
The ECS consists of a series of receptors, enzymes, and our own internal cannabinoids. Molecules such as THC closely mimic our endocannabinoids on a molecular level, allowing them to bind to the same receptor sites.
By activating or blocking these receptors, external cannabinoids such as THC, CBD, and others have access to the largest regulatory system within the human body. Here, they manage to influence many other bodily systems, sometimes in a way that might help to reduce the impact of diseases such as cancer.
Antitumor effects of cannabinoids
Early research suggests that cannabinoids may directly inhibit the initiation, growth, and spread of cancer cells. CBD demonstrates the ability to inflict apoptosis upon cervical cancer cells — a process that makes rouge cells self-destruct. Cannabinoids also appear to disrupt cancer cell growth through other mechanisms, such as reducing their ability to lay down new blood vessels, move, and invade other areas of the body.
Anti-inflammatory effects of cannabis
Inflammation underpins many states of chronic disease and stems from a myriad of factors, including diet and stress. This biological process gives rise to oxidation, which goes on to cause DNA damage — a hallmark of cancer.
Through their antioxidant actions, many cannabis phytochemicals work to neutralise free radicals, reduce cellular damage, and quench the inflammatory process.
Cannabis and the microbiome
Our bodies house more microbes than they do human cells. Over 40 trillion bacteria — consisting of 1,000 different species — form a symbiotic alliance with the human body. They help us digest food, combat infections, and contribute to brain health.
A disturbance in our intestinal flora, known as gut dysbiosis, increases the risk of systemic inflammation and colorectal cancer. The ECS plays a key role in interacting with our microbiome and actively opposes dysbiosis. In animal models, administration of THC amazingly prevents changes in gut microbiota that promote obesity. Instead, the cannabinoid promotes bacteria associated with leanness.
Smoking cannabis appears to reduce cancer risk
Based on this thorough meta-analysis of research papers, smoking cannabis appears to actually decrease the risk of certain cancers. However, many different variables play a role in cancer risk. Smoking any substance exposes the body to harmful chemicals that have the potential to give rise to disease. Interestingly, cannabis also delivers a plethora of molecules that help to prevent such damage.
Many cancer sufferers are deciding to give up conventional approaches altogether and opt for alternatives such as cannabis therapy — although some medical professionals advise against such a move. In this context, smoking cannabis only delivers very small quantities of beneficial phytochemicals, whereas high-potency extracts offer much larger doses.
Luke Sumpter is a freelance journalist that specializes in health, wellness, and alternative therapies. Currently, he’s working on a dissertation exploring the emerging role of the endocannabinoid system in orthopaedic medicine.