Re: ISTOOK: The blunt truth — White house drug czar contradicts Obama on marijuana
Cancer Risk
A number of studies have yielded conflicting evidence regarding the risks of various cancers associated with Cannabis use.
A pooled analysis of three case-cohort studies of men in northwestern Africa (430 cases and 778 controls) showed a significantly increased risk of lung cancer among tobacco smokers who also inhaled Cannabis.[5]
A large, retrospective cohort study of 64,855 men aged 15 to 49 years from the United States found that Cannabis use was not associated with tobacco-related cancers and a number of other common malignancies. However, the study did find that, among nonsmokers of tobacco, ever having used Cannabis was associated with an increased risk of prostate cancer.[6]
A population-based case-control study of 611 lung cancer patients revealed that chronic low Cannabis exposure was not associated with an increased risk of lung cancer or other upper aerodigestive tract cancers and found no positive associations with any cancer type (oral, pharyngeal, laryngeal, lung, or esophagus) when adjusting for several confounders, including cigarette smoking.[7]
A systematic review assessing 19 studies that evaluated premalignant or malignant lung lesions in persons 18 years or older who inhaled marijuana concluded that observational studies failed to demonstrate statistically significant associations between marijuana inhalation and lung cancer after adjusting for tobacco use.[8]
With a hypothesis that chronic marijuana use produces adverse effects on the human endocrine and reproductive systems, the association between marijuana use and incidence of testicular germ cell tumors (TGCTs) has been examined.[9-11] Three population-based case-control studies report an association between marijuana use and elevated risk of TGCTs, especially nonseminoma or mixed-histology tumors.[9-11] However, the sample sizes in these studies were inadequate to address marijuana dose by addressing associations with respect to recency, frequency, and duration of use. These early reports of marijuana use and TGCTs establish the need for larger, well-powered, prospective studies, especially studies evaluating the role of endocannabinoid signaling and cannabinoid receptors in TGCTs.
A comprehensive Health Canada monograph on marijuana concluded that while there are many cellular and molecular studies that provide strong evidence that inhaled marijuana is carcinogenic, the epidemiologic evidence of a link between marijuana use and cancer is still inconclusive.[12]
National Cancer Institute, National Institutes of Health
http://www.cancer.gov/cancertopics/pdq/cam/cannabis/healthprofessional/page5