Wellington, New Zealand: Smoking cannabis, even long-term, is not associated with an increased risk of developing cancers of the head or neck, according to the results of a case control population-based study published in the March 2008 issue of the journal Otolaryngology - Head and Neck Surgery.

Investigators at the Medical Research Institute in Wellington assessed the relative risk of head and neck cancer associated with cannabis smoking in 75 cases (16 of which reported having used cannabis) and 319 controls. Researchers reported that cannabis use - including chronic use of the drug - was not associated with any increased cancer risk compared to non-using controls.

"This population-based study did not find a statistically significant increase in the risk of head and neck cancer in adults [under age 55] from cannabis," authors concluded. "[Even] the risk associated with the highest tertile of cannabis use (defined as one joint a day for more than eight years) was not statistically significant after adjustment for cofounding variables including tobacco smoking, alcohol consumption, and level of income."

By contrast, investigators reported that heavy alcohol use was associated with a nearly six-fold increased cancer risk compared to controls.

In February, a parallel study published by the same investigative team reported that subjects who had "ever used" cannabis experienced, on average, no statistically increased risk of lung cancer compared to non-users.

A prior case-control study sponsored by the US National Institute on Drug Abuse of 164 oral cancer patients and 526 controls determined, "The balance of the evidence . does not favor the idea that marijuana as commonly used in the community is a causal factor for head, neck or lung cancer in adults."

More recently, a 2004 clinical trial performed by investigators at Seattle's Fred Hutchinson Cancer Research Center reported "no association" between cannabis use and the incidence of oral carcinoma, "regardless of how long, how much or how often a person has used [cannabis]."

Most recently, a UCLA study of more than 2,200 subjects (1,212 cases and 1,040 controls) reported that cannabis smoking was not positively associated with cancers of the lung or upper aerodigestive tract - even among individuals who reported smoking more than 22,000 joints during their lifetime.

NORML Deputy Director Paul Armentano said that the Wellington team's findings add to the growing body of evidence indicating that smoking cannabis poses a surprisingly low cancer risk compared to the use of tobacco or alcohol. He said: "While studies purporting to uncover alleged harms due to cannabis use receive wide dissemination by the mainstream press, research that fails to find such harms often gets ignored. It will be telling to see if this latest study is the exception or the rule."

Full text of the study, "Cannabis use and cancer of the head and neck: Case-control study," appears in Otolaryngology - Head and Neck Surgery, PubMed, March 2008,
http://www.ncbi.nlm.nih.gov/pubmed/18312888

Additional information on cannabis and cancer risk is available in the online report, "Cannabis Smoke and Cancer: Assessing the Risk," at: http://www.norml.org/index.cfm?Group_ID=6891

NIDA:  http://www.nida.nih.gov/MeetSum/marijuanaabstracts.html

Washington Post story on UCLA study:
http://www.washingtonpost.com/wp-dyn/content/article/2006/05/25/AR2006052501729.html