For the first time, more Americans regularly use cannabis than drink alcohol.
Although smoking weed to get high and relax is considered by many to be a safer alternative to tobacco use or even alcohol consumption, there is no evidence to support the drug’s long-term health effects. What little is known suggests that it may not be as harmless as some think.
A new study from the American Head and Neck Society shows that excessive cannabis use may increase the risk of developing head or neck cancer, including oral, oropharyngeal, nasopharyngeal, salivary gland and laryngeal cancer.
The study’s authors, led by epidemiologist Tyler Gallagher of the University of Southern California in Los Angeles, say their results should be “interpreted with caution” because of the possibility that they did not fully control for alcohol and tobacco use and HPV status – all factors that can increase the risk of developing head or neck cancer.
Additionally, the study did not measure the amount or strength of cannabis consumed by participants, how often it was consumed, or how the cannabis was consumed (whether it was vaporized, smoked, or ingested).
Still, head and neck surgeon Niels Kokot of the University of Southern California says, “This is one of the first studies – and the largest to date – to link head and neck cancer to cannabis use. Identifying this risk factor is important because head and neck cancer may be preventable if people know what behaviors increase their risk.”
The research was based on 20 years of medical records of 116,076 people who had been diagnosed with a cannabis-related disorder that was “severe enough to cause physical or emotional symptoms resulting in an inability to stop cannabis use.”
This group was then compared with a cohort of nearly 4 million people who did not have a cannabis use disorder.
Ultimately, the relative risk of developing head or neck cancer was 3.5 to 5 times higher in people with cannabis use disorder than in people without the disorder.
To put this in perspective, the relative risk of developing head or neck cancer is two to ten times higher for tobacco users than for non-smokers. For alcohol users, the relative risk for mouth and throat cancer is 5.7 and for laryngeal cancer is 3.2.
“Given that our cohort included those with the highest cannabis use, we can assume that the association between cannabis use and the risk of developing HNC found in this study was somewhat smaller than that between alcohol and tobacco use,” conclude Gallagher and his colleagues.
The results are intriguing, but more research is needed to determine whether this association is causal and what mechanisms might be at play. The current cohort was assumed to be heavy cannabis users because of their diagnosis of cannabis use disorder, but their actual use was never properly measured.
Previous clinical trials examining the link between cannabis use and head and neck cancer have had mixed results. Most studies found no link, even after following cannabis users for up to eight years.
Earlier this year, the U.S. Drug Enforcement Agency announced plans to relax federal restrictions on cannabis, reclassifying it from a Schedule I drug to the less stringent Schedule III.
Scientists hope this move will remove some of the current barriers to cannabis research and make the field more accessible like never before.
The study was published in JAMA Otolaryngology – Head and Neck Surgery.
