The long-term health effects of cannabis use disorder (CUD), which is commonly observed in the United States (U.S), are still not fully understood. This study evaluated the relationships between CUD and the risk of oral cancer over five years in this clinical cohort research. When cannabis is burned, it releases polycyclic aromatic hydrocarbons, which are also present in tobacco smoke. From 6 academic medical institutions, clinical records were examined in this retrospective cohort study by using data from the University of California.
Adults without any prior diagnosis of oral cancer were included in the study from January 2012 to December 2019. Data were collected till December 2024 because patients are monitored up to five years for diagnosis of tongue or lip cancer. The Diagnostic and Statistical Manual of Mental Disorders was observed in those using 14 joints per week. Adjusted odds ratios (ORs) for the incidence of oral cancer were estimated using multivariable logistic regression. The relationship between CUD and time to diagnose cancer was assessed using Cox proportional hazards regression. Complete case data analysis was carried out using R version 4.2.3.
This study was exempted from the protection of human subjects by the University of California Health System Institutional Review Board (protocol 1604619-1). Over the five-year follow-up, 949 cases out of 45,129 patients met the criteria for a new diagnosis of CUD. The average age was 44.5 years, and 54% were female subjects in the cohort. A total of 106 individuals were diagnosed with oral cancer throughout the follow-up period. The result of unadjusted logistic regression showed that CUD was associated with a higher risk of oral cancer with an OR of 3.24 and a 95 % confidence interval (CI) of 1.50-7.00.
In a subgroup study of tobacco users, oral cancer rates were higher among tobacco users with CUD as compared to those without the disease. In the CUD group, the time to diagnosis of oral cancer has an unadjusted hazard ratio (HR) of 3.24. Female sex and high body mass index (BMI) were related to reduced risk, while age was related to increased cancer risk with yearly adjusted HR=1.04 and p<0.01. Cannabis smoke was found to cause cytologic and histologic changes in respiratory tract cells, similar to tobacco.
Studies on animals and in vitro suggest that cannabis smoking might cause cancer. Condensation products from cannabis have been shown to cause chromosomal abnormalities and DNA damage in mammalian cells. Social and behavioural risk factors such as tobacco use, alcohol intake, and a lack of participation in preventive healthcare overlap in CUD patients. The connection between CUD and oral cancer highlighted the importance of incorporating oral health education in counselling and treatment for substance use disorders.
Data on use patterns in this cohort study cannot be analysed because of inconsistent documentation in structured fields. The study has limitations due to its dependence on diagnostic codes, which show improper prevalence of mouth cancer and cannabis consumption. Further studies are essential to evaluate the long-term carcinogenic risks associated with chronic cannabis use.
Reference: Cuomo RE. Cannabis use disorder and five-year risk of oral cancer in a multicenter clinical cohort. Prev Med Rep. 2025;57:103185. doi:10.1016/j.pmedr.2025.103185
