Study: History Of Cannabis Use Associated With Reduced Cancer Risk

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by Paul Armentano

on February 6, 2015

Cannabis use is inversely associated with incidences of bladder cancer in males, according epidemiological findings published in the February issue of the journal Urology.

Investigators at the Kaiser Permanente Los Angeles Medical Center, Department of Neurology assessed the association of cannabis use and tobacco smoking on the risk of bladder cancer in a multiethnic cohort of more than 80,000 men aged 45 to 69 years old over an 11-year period.

Researchers determined that a history of cannabis use was associated with a decreased risk of bladder cancer. By contrast, tobacco use was associated with an increased risk of cancer.

“After adjusting for age, race or ethnicity, and body mass index, using tobacco only was associated with an increased risk of bladder cancer (hazard regression 1.52) whereas cannabis use was only associated with a 45 percent reduction in bladder cancer incidence (HR 0.55),” investigators reported.

Subjects who reported using both tobacco and cannabis possessed a decreased risk of cancer (HR 1.28) compared to those subjects who used tobacco only (HR 1.52).

The study is the first to indicate that cannabis use may be inversely associated with bladder cancer risk.

Authors concluded:

“In this multiethnic cohort of 82,050 men, we found that cannabis use alone was associated with a decreased risk of bladder cancer. … [M]en who used tobacco alone were 1.5 times more likely to develop bladder cancer when compared with men who did not use tobacco or cannabis… However, among men who used both substances, this risk of bladder cancer was mitigated… If this represents a cause and effect relationship, this pathway may provide new opportunities for the prevention and/or treatment of bladder cancer.”

In 2009, Brown University researchers similarly reported that the moderate long-term use of marijuana was associated with a reduced risk of head and neck cancers in a multi-center cohort involving over 1,000 subjects. Investigators further reported that marijuana use “modified the interaction between alcohol and cigarette smoking, resulting in a decreased HNSCC (head and neck squamous cell carcinoma) risk among moderate smokers and light drinkers, and attenuated risk among the heaviest smokers and drinkers.”

Read the abstract of the study, “Association between cannabis use and the risk of bladder cancer: Results from the California Men’s Health Survey,” online here.

This piece first appeared on the NORML Blog.

Paul Armentano is the deputy director of NORML and co-author of  the book, ‘Marijuana Is Safer, So Why Are We Driving People to Drink?’