A long term study in New Zealand followed 1,000 people from birth to age 38, allowing researchers to examine what negative impact marijuana use may have on physical health, and they found the impact is pretty minor. The study looked at an incredibly broad spectrum of health indicators such as lung function, systemic inflammation, body mass index, waist size, cholesterol, glucose control, etc… The only physical health problem that correlated with marijuana use was an increased level of gum disease. Otherwise, marijuana smokers’ physical health indicators were basically on par with everyone else in their age group.
From purely a physical health perspective (mental health was examined separately), this indicates that smoking marijuana might fall on the spectrum of bad behavior somewhere between sloppy toothbrushing and not visiting the dentist regularly. By comparison, the same data showed that tobacco smoking was not only associated with increased gum disease but also numerous more serious health issues including reduced lung function and bad metabolic health indicators. This study is inline with several other studies which have found significant health problems from tobacco or alcohol use but relatively few physical problems from marijuana use.
The study didn’t set out to examine why marijuana use was correlated with worse gum health, but the most likely explanations fall into three broad categories. First, it is possible that it is the act of smoking which is bad for the gums. The fact that smoking tobacco is also associated with gum issues gives some weight to this hypothesis. If the cause is smoking itself, it might be possible for individuals to reduce or eliminate this potential physical health issue by using alternative methods of ingesting marijuana, such as vaporizing or edibles.
Second, it could be something unique to marijuana, such as THC or some other cannabinoid, that is causing issues for the gums. For example, many people do complain of “cottonmouth” from marijuana use, so maybe this mouth dryness is causing problems for gum health.
Finally, there is the small possibility this is simply a correlation without causation. The statistical analysis used tried to account for likely confounding variables, but they still could have missed something unexpected. For example, maybe people who enjoy marijuana also are more likely to enjoy a particular acidic food.
More research will be needed to verify if there is a connection and what the cause might be, but in light of this new study it would be advisable for anyone who smokes marijuana to try to be diligent about brushing, flossing, and visiting a dentist regularly — good advice for anyone, whether they enjoy marijuana or not.