Head and neck cancer among marijuana users: A meta-analysis of matched case–control studies

•Meta-analysis used to assess association between marijuana use and HNC.•Nine case–control studies were used after selection in seven databases.•The amount of marijuana users was similar between cancer patients and controls.•There is no association even excluding tobacco influence.•Cancer site and frequency of marijuana use may influence that association.

ObjectivesThe scientific literature presents conflicting data on a possible causal relationship between marijuana users and the development of head and neck cancer.DesignThis study performed a systematic review with meta-analysis. Articles were selected from various electronic databases using keywords obtained from the Medical Subject Headings (MeSH). After reading by three reviewers and scoring of methodological quality, six articles (totaling nine case–control studies) were assessed with Comprehensive Meta-Analysis® software. The value of effect (odds ratio) was calculated, which represented the chance of developing head and neck cancer between individuals who had smoked marijuana in their lifetime in models controlled for age, gender, race, and tobacco consumption.ResultsApproximately 12.6% of cases and 14.3% of controls were marijuana users. The meta-analysis found no association between exposure and disease (OR = 1.021; IC 95% = 0.912–1.14; p = 0.718).ConclusionNo association between lifetime marijuana use and the development of head and neck cancer was found. The different methods of collection/presentation of results in the selected articles prevented other analyzes from being conducted. Additional studies are needed to assess for long-term effects.