A large meta-analysis in the United States has explored the relationship between cannabis use and cancer risk. Delivering what may be surprising results to some, the study found that cannabis use decreased the risk of cancer in study participants for all observed cancers but one—testicular cancer. This suggests that the beneficial compounds of cannabis could outweigh those from carcinogenic smoke.
Cannabis smoke contains ingredients that have anticancer properties – the best known are THC and CBD. But it also contains substances that increase the risk of cancer, including nitrosamines and polycyclic aromatic hydrocarbons.
It is not yet clear how this combination affects cancer risk. According to a detailed meta-analysis of all studies conducted on the subject to date, a researcher from the Department of Biological Sciences at Indiana University in South Bend, USA, concludes that smoking cannabis significantly reduces the risk of cancer in the USA (Clark 2020).
However, in order to make optimal use of the cancer-inhibiting properties of cannabis, cannabis should not be smoked. It should be vaporized, or taken orally. A total of 34 studies were considered.
Quality control in the meta-analysis
The results show a trend towards a reduced risk of developing cancer from smoking cannabis by about 10 percent. If studies with a high probability of bias were excluded, the reduced risk was statistically significant at 14 percent.
The author assumed a high probability of studies distorting the results if the studies were from North Africa, or if tobacco consumption was not taken into account, or where there were fewer than 20 cases sampled.
Not all cancers affected equally by cannabis use
For testicular cancer, there was a non-significant increase in cases of 12 percent. Yet, even after the additional risk for testicular cancer, the remaining data still showed a significant overall decrease in risk by 13 percent.
Cancers of the head and neck showed a highly significant decrease in cancer risk of 17 percent while, for other cancers like lung cancer, there were no significant differences between cannabis smokers and non-smokers.
In summary, only testicular cancer showed a tendency towards a slightly increased risk, but this was not statistically significant. For all other cancers, there was a tendency to a slightly decreased risk, but this was only statistically significant for head and neck cancer. The author wrote that the “current analysis suggests that cannabis use in the United States could reduce the risk of cancer by 10 % (…). “
The results of the study
Given the importance of cancer in the total number of deaths in the United States – about 600,000 people die of cancer every year in the United States – the authors point out that “cannabis use could significantly reduce the cancer-related death rate in the United States. However, the available data gives little confidence in this conclusion. There appear to be different responses among cancers and, for many cancers, there is little or no data available.”
In addition to the great variation in results between different studies and other factors, the author notes that although a relationship between cannabis and cancer can be demonstrated, “no causality can be established. Therefore, caution is needed when interpreting these data. Nevertheless, the data suggest that cannabis use may reduce cancer risk in the United States.”
Reduced risk of cancer due to cannabis use not surprising
A reduced risk of cancer in cannabis users should not come as a surprise, as cannabis and cannabinoids reduce obesity, inhibit chronic inflammation, lower fasting insulin levels and insulin sensitivity, and have direct anti-tumor effects. These are all factors that can have a beneficial effect on the development of cancer.
In addition, the respiratory tract and bladder would be exposed to the highest concentrations of carcinogens of cannabis smoke, but the risk of cancer of the mouth, throat, larynx, and bladder is significantly reduced in cannabis users. This shows that the carcinogenic effects of cannabis constituents outweigh the carcinogenic effects of cannabis smoke itself in the respiratory tract and bladder, where exposure to carcinogens is high.
Cannabis contribution to reduced cancer risk could be greater than initial estimate
It is possible that the actual reduction in cancer risk from cannabis use is even greater than the estimated 10 percent reduction in risk that emerges from the current analysis.
This is because there is little data on the effects of cannabis use on the relative risk of cancers other than those that are exposed to the carcinogens of smoke, such as those associated with obesity, such as cancer of the liver, breast, colon, stomach, and prostate. There are also studies that show that regular cannabis users are less obese and have a lower body mass index.
More data is needed to explore effects of cannabis on other cancers
Some cancers are relatively common, while others are rare, and some types have a much higher mortality rate than others. In the current data set, only testicular cancers show a trend towards an increased risk among cannabis users, and testicular cancer is a relatively rare cancer with a high survival rate.
For many other cancers, there is little to no data on the association with cannabis use. The actual impact of cannabis use on cancer cases and deaths can therefore not be estimated with certainty using the data currently available. The author of the review points out that “given the large number of cancer diagnoses and the large number of people who use cannabis, however, even a moderate effect on cancer risk will have a significant public health impact.“
This article was written by a third party contributor and does not reflect the opinion of Hemp.im, its management, staff or its associates. Please review our disclaimer for more information.
This article may include forward-looking statements. These forward-looking statements generally are identified by the words “believe,” “project,” “estimate,” “become,” “plan,” “will,” and similar expressions. These forward-looking statements involve known and unknown risks as well as uncertainties, including those discussed in the following cautionary statements and elsewhere in this article and on this site. Although the Company may believe that its expectations are based on reasonable assumptions, the actual results that the Company may achieve may differ materially from any forward-looking statements, which reflect the opinions of the management of the Company only as of the date hereof. Additionally, please make sure to read these important disclosures.
First published in Hanf Journal, a third-party contributor translated and adapted the article from the original. In case of discrepancy, the original will prevail.
Although we made reasonable efforts to provide accurate translations, some parts may be incorrect. Hemp.im assumes no responsibility for errors, omissions or ambiguities in the translations provided on this website. Any person or entity relying on translated content does so at their own risk. Hemp.im is not responsible for losses caused by such reliance on the accuracy or reliability of translated information. If you wish to report an error or inaccuracy in the translation, we encourage you to contact us.