• Photo for New Study: Heavy Marijuana Use Linked to Testicular Cancer
    Photo Credit: iStockPhoto

New Study: Heavy Marijuana Use Linked to Testicular Cancer

By L. K. Regan

Over the last 50-odd years, rates of testicular cancer have consistently risen. And, over the same period, marijuana use in North America, Europe, and Australia/NewZealand has increased at pretty much the same rate. Now, researchers at the Fred Hutchinson Cancer Research Center in Seattle have concluded that that’s not just coincidence: regular smoking of marijuana increases men’s risk of the most aggressive form of testicular cancer. Now, that is a buzz-kill.

For the study, published in the February 9 edition of the journal Cancer, co-authors Stephen M. Schwartz and Janet R. Daling interviewed 369 men from the Seattle/Puget Sound area, all between the ages of 18 and 44, and all of whom had been diagnosed with testicular cancer. The men were asked to describe the frequency and duration of their history of marijuana use, as well as other possible cancer-causing behaviors like drinking alcohol and smoking tobacco. For comparison, the researchers also interviewed 979 randomly selected men of the same age range and locale. The results were enough to make anyone paranoid: being a regular toker came with a 70 percent increase in the risk of testicular cancer. The risk was highest for anyone who smoked at least once a week, and/or who started a long-term habit as a teenager. Worse yet, the effect appears to be limited to nonseminoma, the most aggressive form of testicular cancer, which tends to impact younger men between the ages of 20 and 35 years and that accounts for about 40 percent of all testicular cancer cases.

Why is nature harshing the mellow? The researchers have two theories. For one thing, though the brain is the best known receptor for THC (tetrahydrocannabinol), the active chemical in marijuana, there are also receptors in the spleen, uterus, immune-system cells—and testicles. But the testicles produce a cannabinoid chemical of their own that may help to ward off cancer and with which marijuana may interfere, allowing the formation of tumors the body would otherwise fight off.

Of course, many men develop a pot habit while in their teens, when there is plenty of time for staring at the ceiling and listening to music. And a history of marijuana use in adolescence was associated with the highest rates of cancer. This may be because, the researchers say, testicular cancer appears to have its roots in the womb, when some testicular cells (called fetal germ cells) develop improperly. During puberty and early adulthood, the presence of male sex hormones turns these cells malignant. So, says Daling, “Just as the changing hormonal environment of adolescence and adulthood can trigger undifferentiated fetal germ cells to become cancerous, it has been suggested that puberty is a 'window of opportunity' during which lifestyle or environmental factors also can increase the risk of testicular cancer. This is consistent with the study's findings that the elevated risk of nonseminoma-type testicular cancer in particular was associated with marijuana use prior to age 18.”

As a result of these findings, study author Schwartz is particularly concerned about the impact for younger men. "What young men should know,” he says, “is that first, we know very little about the long-term health consequences of marijuana smoking, especially heavy marijuana smoking; and second, our study provides some evidence that testicular cancer could be one adverse consequence. So, in the absence of more certain information, a decision to smoke marijuana recreationally means that one is taking a chance on one's future health." All of which gives a new and unfortunate meaning to the term “burn-out”.