New research published in the journal Cancer describes an increased risk for testicular cancer in men who smoked marijuana. The study (abstract here) looked at two types of testicular cancer, the easier-to-treat seminoma (no increased risk) and the more difficult type of cancer, non-seminoma, which showed a doubling of risk.
Researchers controlled for other risk factors, such as education level, history of an undescended testicle, use of cocaine and other drugs. The results showed smoking marijuana was a relevant factor.
The study was meant to address a couple of trends seen in the general population to see if they may be related. The incidence of testicular cancer has increased, and the number of men smoking marijuana has also increased. Unfortunately, the study wasn’t specific enough to tease out how much marijuana is significant, nor how length of use matches up with risk. The study had 163 participants, which wasn’t enough to get much detail on what other lifestyle choices may be influencing risk.
The method used – interviewing people with a diagnosis of testicular cancer about their lifestyle choices – is only useful generally. The danger in this type of study is coming up with an association by chance. For example, in this research, a person’s participation in religion was identified as a risk factor and cocaine use came out as lowering risk. This means that, while interesting, the study will have to be repeated in a larger population to determine how robust the findings are.
Now that marijuana use is legal in several states, we can expect these types of studies to increase – it’s easier to find users, and they are more willing to discuss their use. There’s also an incentive for medical authorities to request more information about the effects of marijuana use as they grapple with legalization issues. How harmful is weed really? That question hasn’t been answered in a solid scientific way.