Smoking cannabis does not appear to increase the user's risk of head and neck cancers, according to a new study by New Zealand and British researchers.
The small study found that found that among 75 cases of head and neck cancer, the relative risk of smoking cannabis and contracting head and neck cancer in marijuana users was the same (1.0) as in those who had never smoked cannabis.
There were 319 patients used as "controls" to compare the risks.
There were greater relative risks of contracting the cancers among tobacco smokers (2.1) and heavy drinkers of alcohol (5.7), compared with patients who had abstained from those activities.
But the New Zealand researchers at the Medical Research Institute and Otago University recommended repeating the study with larger numbers of subjects.
Their study was reported this week in the March 2008 issue of the Otolaryngology journal on head and neck surgery.
Cancers of the head and neck, with more than 500,000 new cases diagnosed each year worldwide, represent the fourth-most common type of cancer.