While this type of study cannot conclusively prove cause and effect, the combination of this new study and existing research — which for decades has shown that cannabinoids are fairly potent anticancer drugs — raises a significant possibility that marijuana use is in fact protective against certain types of cancer.
A team of researchers from several major universities conducted what is known as a “case-control” study, comparing patients who had squamous cell carcinoma of the mouth, larynx, and pharynx with control patients matched for age, gender, and residence location who did not have cancer. By looking at matched groups with and without cancer, researchers hope to find patterns indicating risk or protective factors. In this case they focused on marijuana use, but also took into account known risk factors for this type of cancer, including tobacco and alcohol use.
After adjusting for those confounding factors, current marijuana users had a 48% reduced risk of head and neck cancer, and the reduction was statistically significant. Former users also had a lower risk, though it fell short of being significant. The investigators crunched the numbers several different ways — for example, by amount of marijuana used or the frequency of use — and the findings stayed the same nearly across the board, with moderate users showing the strongest and most consistent reduction in cancer risk.
The scientists write, “We found that moderate marijuana use was significantly associated with reduced risk HNSCC [head and neck squamous cell carcinoma]. The association was consistent across different measures of marijuana use (marijuana use status, duration, and frequency of use).”
Strikingly, among drinkers and cigarette smokers, those who also used marijuana reduced their cancer risk compared to those who only drank and smoked cigarettes. So marijuana may actually have been countering the known bad effects of booze and cigarettes.