NEW YORK (Reuters Health) Aug 25 - Marijuana use for 10 to 20 years is associated with a 62% reduced risk of head and neck squamous cell carcinoma (HNSCC), the results of a population-based case-control study suggest.
However, further research from larger studies is needed to verify this association, the researchers emphasize. Moreover, even if marijuana use were found to protect against this malignancy, the risks of use may still outweigh this benefit.
"Marijuana is an entry-level drug and can be associated with later use of more serious addictive drugs, as well as other risk behaviors," Dr. Karl T. Kelsey, from Brown University, Providence, Rhode Island, and colleagues note. "Any policy regarding marijuana use should take these into consideration and should not be made based on one study's results."
The new study, reported in the August issue of Cancer Prevention Research, featured 434 patients with HNSCC and 547 matched controls seen in the Greater Boston area from December 1999 to December 2003. Lifetime marijuana use was assessed via questionnaire.
After adjusting for smoking, drinking, and other potential confounders, use of marijuana from 0.5 to 1.5 times per week was associated with a 48% reduced risk of HNSCC compared with less frequent use. This association was independent of human papillomavirus 16 antibody status.
Marijuana use starting at an older age appeared to confer greater protection against HNSCC than use beginning at a younger age. Relative to never users, those who began using marijuana between the ages of 15 and 19 years were 47% less likely to develop HNSCC, while users who began at age 20 or older had a 61% reduced risk (p trend <>
As to possible mechanisms for these associations, the authors note that cannabinoids have been shown to have antitumor effects and can influence cellular signaling.
Cancer Prev Res 2009;2:759-768.
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