Cocaine, on the other hand...
PROBLEM: Testicular germ cell tumors (TGCTs), already the most common cancer in men aged 15 - 45, are being diagnosed at rising rates. Also noted to be on the rise in this demographic is marijuana use. Since 1) scientists have reason to believe that men are most vulnerable to TGCT risk factors during puberty, 2) research has suggested that some of the stuff found in marijuana smoke may be one of those risk factors, and 3) marijuana use is especially high among younger males, there just might be a connection.
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METHODOLOGY: A population of 163 men in Los Angeles County, California who had been diagnosed with TGCT between 1986 and 1991 participated in the study. Each subject was matched for age, race, ethnicity, and neighborhood of residence at time of diagnosis with up to four controls. Interviewers were sent to the participants' homes to ask them about basic demographic information, family and personal disease history, and personal use of tobacco, alcohol, and recreational drugs.
RESULTS: After adjusting for education, religiosity, history of cryptorchidism (undescended testicle -- a known risk factor for TGCT), and use of cocaine and amyl nitrite (a.k.a. poppers), people who had ever used marijuana had nearly twice the risk of developing testicular germ cell tumors compared to those who had never smoked up. When parsed out, the risk of developing nonseminoma (the more difficult to cure version of the cancer) was more than doubled, but did not increase significantly for seminoma.
Most likely due to the relatively small sample size, the results get a bit messy after this and don't show any clear association between how much or how frequently subjects used and their risk of TGCT. Risk was decreased for more frequent users, nonsignificant for those who used for over ten years or continued to use, and more than doubled for those who used to smoke, but no longer do. Those who reported using marijuana less than once per week or for fewer than ten years were at more than twice the risk of those who never touched the stuff.
And because the interviewers asked so many questions, some other interesting (if not strictly relevant) findings emerged -- like how the median duration of mushroom use was two years and the people who had been diagnosed with TGCT were less likely than controls to report religious affiliation. Another downplayed but intriguing finding was that cocaine users actually had a reduced likelihood of developing testicular cancer.
CONCLUSION: From the above results, combined with previous studies, the authors conclude that they can confirm "the epidemiological association of marijuana use with TGCT risk," specifically for nonseminomatous tumors. Broadly, the mechanism at play may be due to the fact that human cannabinoid receptors (to which, you may be able to guess, THC binds) are expressed in the pituitary, hypothalamus, and male reproductive system. Although far less research has been done on the subject, the authors also hypothesize that cocaine may kill germ cells, explaining the negative association that was found.
IMPLICATIONS: TGCT is largely treatable, but treatment usually involves have the afflicted testis removed.The authors also suggest that cocaine may play a role in opposing the effects of THC. This is presented as bad news, because it could mean that the risk of TGCT from marijuana use is even greater than doubled, but was controlled for by cocaine use in their hard-partying subjects. But presumably, if you like both drugs, this could be spun as the silver (or snowy white) lining to your cloud of cancer-causing weed smoke.
The full study, "Population-based case-control study of recreational drug use and testis cancer risk confirms an association between marijuana use and nonseminoma risk ," will be published in the journal Cancer .