Providence, RI: The moderate long-term use of marijuana is associated with a reduced risk of head and neck cancers, according to the results of a population-based case-control study published online by the journal Cancer Prevention Research.

Investigators at Rhode Island’s Brown University, along with researchers at Boston University, Louisiana State University, and the University of Minnesota assessed the lifetime marijuana use habits of 434 cases (patients diagnosed with head and neck squamous cell carcinoma from nine medical facilities) compared to 547 matched controls.

Authors reported, “After adjusting for potential confounders (including smoking and alcohol drinking), 10 to 20 years of marijuana use was associated with a significantly reduced risk of head and neck squamous cell carcinoma … [as was] moderate weekly use.”

Subjects who smoked marijuana and consumed alcohol and tobacco (two known high risk factors for head and neck cancers) also experienced a reduced risk of cancer, the study found.

“Our study suggests that moderate marijuana use is associated with reduced risk of HNSCC,” investigators concluded. “This association was consistent across different measures of marijuana use (marijuana use status, duration, and frequency of use). … Further, we observed that marijuana use modified the interaction between alcohol and cigarette smoking, resulting in a decreased HNSCC risk among moderate smokers and light drinkers, and attenuated risk among the heaviest smokers and drinkers. … Despite our results being consistent with the point estimates from other studies, there remains a need for this inverse association to be confirmed by further work, especially in studies with large sample sizes.”

A separate 2006 population case-control study also reported that lifetime use of cannabis was not positively associated with cancers of the lung or aerodigestive tract, and noted that certain moderate users of the drug experienced a reduced cancer risk compared to non-using controls.

By contrast, a study published earlier this week in the journal Cancer Epidemiology reports that even the moderate use of alcohol (six drinks or less per week) is associated with an elevated risk of various cancers – including stomach cancer, rectal cancer, and bladder cancer.

For more information, please contact Paul Armentano, NORML Deputy Director, at: paul@norml.org. Full text of the study, “A population-based case control study of marijuana use and head and neck squamous cell carcinoma,” will appear in Cancer Prevention Research.