Background: Although marijuana is the most abused illicit drug in the United States, very little is known about the effect of marijuana on oral health.

Objective: To examine the association of recreational marijuana use (both singly and with other substances) with dental caries.

Methods: Data included 4517 individuals who were 18 years or above and received dental caries examination from 2013-2014 National Health and Nutrition Examination Survey, which provides a nationally representative estimate. Outcome was a binary variable of dental caries, and primary independent variable was marijuana use. A multivariable logit model was employed, adjusting demographics, socioeconomic status, and other substance use.

Results: Among the applicable study population, 39% (n=1987) were marijuana users with a higher likelihood of dental caries among elderly, Hispanics, people with lower educational status and smokers (p < 0.05 for all). Marijuana users than non-users (adjusted odds ratio [aOR] 1.75; 95% confidence interval [CI] 1.09-2.82) and Hispanics than non-Hispanic whites (aOR 1.86; 95% CI 1.09-3.18) were more likely to have dental caries. Among marijuana users, tobacco (aOR 1.5, 95% CI 1.21-1.88) and cocaine users (aOR 1.48, 95% CI 1.12-1.97) had higher risks of dental caries.

Discussion: Given the increased dental health risks due to the legalization of recreational marijuana in 11 states and District of Columbia, this study would provide valuable insights to patients, dental practitioners, and health policy makers who are interested in improvement of relevant counselling, treatment, and health outcomes.