Smoking cannabis has long been associated with poor oral health. Cannabis has received blame for increased rates of gum disease, from Kiwi young adults to the Hadza foragers of Tanzania. Now a recent report out of Columbia University College of Dental Medicine has added a population of American adults to the list. However, limitations to the study may lead to more questions than answers.

The report investigated the association between “frequent recreational cannabis use” -- which was defined as marijuana or hashish consumption at least once per month for 12 months -- with symptoms of gum disease. Consistent with previous reports, the researchers found an increased rate of periodontitis, which is the inflammation and destruction of the gums around the tooth and weakened bone density of the tooth socket, in frequent cannabis users.

The study benefited from a large sample size (519 frequent recreational cannabis users were compared against 1419 non-frequent users) and its ability to control for several variables such as income level, alcohol use, and tobacco use. These statistical techniques allowed researchers to identify the contribution of these variables in risk for developing periodontitis. This contribution was then statistically removed to reveal the effect of cannabis use by itself. In the end, it was clear that cannabis still reduced oral health. Or so the authors claimed.

If you find yourself getting lectured by the oral hygienist, with your mouth open as they scrape away, there are several limitations to the study that you can spit back (once they put down all the sharp tools, of course). Let’s start with alcohol as a confounding factor.

1. Alcohol Consumption

It’s widely accepted that regular alcohol use reduces oral health. To control for alcohol use in this study, participants were grouped into alcohol users (i.e. those who consumed 12 or more drinks a year) and non-users. This massive range of alcohol consumption patterns makes it especially challenging to identify its overall contribution to periodontitis in this study. The result could potentially artificially inflate cannabis’ contribution to poor oral health.

2. Dental Services

Another limitation is that the survey failed to sufficiently account for professional dental services. To inquire about dental treatment, participants were solely asked if they had received a single treatment for gum disease within the last year. Since professional dental services are recommended at minimum every 6 months, this assessment doesn’t adequately capture the quality of professional treatment the participants received throughout their years of cannabis use. Since cannabis users generally report seeking fewer professional health services, it’s unclear if cannabis itself resulted in poorer oral health, or if users just failed to seek regular professional dental treatment.

3. Method of Consumption

The most glaring limitation is the failure to account for method of cannabis consumption. Given the link between tobacco smoking and poor oral health, the route of consumption may be just as important as what’s being consumed. While cannabis is traditionally smoked, the proportion of cannabis consumption from vaping or eating cannabis products is on the rise. Without controlling for consumption method, it’s still too early to draw any conclusions regarding the impact of the phytocannabinoids themselves (of which THC and cannabidiol are two of many) on oral health. It may end up being that vaping or eating cannabis leads to better overall oral health outcomes than smoking the plant. But this remains to be tested.

4. Cannabis Could Treat Gum Disease

Despite research indications linking cannabis use to poor oral health, animal studies have suggested that cannabidiol, a non-psychoactive constituent of cannabis, may protect against bone density loss in periodontitis. Scientists from Brazil revealed that cannabidiol protected against bone loss at the tooth socket that’s associated with experimental periodontitis in rats. This protection likely stemmed from cannabidiol’s anti-inflammatory properties. Indeed, many of the inflammatory markers associated with periodontitis were reduced in cannabidiol-treated rats.

So while the cannabis plant is associated with reduced oral health, the route by which it does so remains unclear. And in the end, it may also end up also possessing the secrets to treatment. Several products have already sprung up to suggest such a link, including this marijuana toothpaste