“The scientific literature presents conflicting data on a possible causal relationship between marijuana users and the development of head and neck cancer.

This study performed a systematic review with meta-analysis.

The meta-analysis found no association between exposure and disease.

No association between lifetime marijuana use and the development of head and neck cancer was found.”

http://www.ncbi.nlm.nih.gov/pubmed/26433192

http://www.aobjournal.com/article/S0003-9969(15)30041-8/abstract