In a recent study, Thomas M. Clark, Ph.D., head of a recent analysis, found that “the anticancer effects of cannabis outweigh the carcinogenic effects even in the airways and bladder, where carcinogen exposure is high.” 

Clark headed an August analysis directly on the issue of cannabis and cancer, supported by his sabbatical leave from Indiana University South Bend. At first, Clark had three hypotheses: cannabis increases cancer risk, the benefits and risks of using cannabis canceled out, or cannabis lowers cancer risk.  

At the first analysis of the data set, there was a slight association with cannabis and reduced cancer risk. However, by removing data that did not control for tobacco use, defined as data with a high risk for selection bias, and data at risk for performance bias, the association became medium to large.

Likewise, the data revealed a medium to large association with reduced cancer risk if data related to testicular cancer was removed. However, according to the analysis, “the hypothesis that cannabis use increases cancer risk is not supported by the available data.”  

Making Sense of the Complexity of Cancer Risk 

In the words of Clark, “decreased cancer risk in cannabis users should not be surprising, as cannabis and cannabinoids decrease obesity, inhibit chronic inflammation, reduce fasting insulin levels and insulin sensitivity, and have direct antitumor actions.”

The effects cannabis has in fighting obesity are far-reaching and severe. Research on a mouse model found that not only did THC treatment prevent obesity, but it preserved the gut microbial flora, preventing it from mirroring an obese phenotype.

Additionally, cannabis lowers insulin resistance and can act as an anti-inflammatory. Research has proven cannabis’s anti-tumor effects in a laboratory setting.  

According to Clark’s math, cannabis may decrease the risk of cancer by 10%. If that is true, then among the 55 million Americans cannabis users, the substance may prevent as many as 23,800 to 35,700 cancer diagnoses and 8,498 to 12,747 cancer deaths each year.  

While not sufficient treatment in itself, research continues to find cannabis is an excellent tool in the war against cancer.