It's possible that men who frequently smoke marijuana, according to a new study, have a higher risk of testicular cancer than those who do not. However, the researchers say the link is currently a "hypothesis" that needs further testing as no previous studies had found a link between marijuana and the disease.

In a population-based case-control study, men diagnosed with testicular cancer were 70% more likely to be current marijuana users than were healthy controls, according to Stephen Schwartz, Ph.D., of the Fred Hutchinson Cancer Research Center, and colleagues.

The study from scientists at the Fred Hutchinson Cancer Research Center in Seattle is the first to look specifically at marijuana use in relation to the disease. They studied 369 men aged 18 to 44, who had been diagnosed with testicular cancer, and quizzed them about marijuana use. Their replies were compared to those from almost 1,000 apparently healthy control subjects.

Since the 1950s, the incidence of the two main cellular subtypes of testicular cancer, nonseminoma and seminoma – the more common, slower growing kind that strikes men in their 30s and 40s – has increased by 3 percent to 6 percent per year in the U.S., Canada, Europe, Australia and New Zealand. During the same time period, marijuana use in North America, Europe and Australia has risen accordingly. Marijuana is also being examined as a culprit because it decreases sperm formation.

Nevertheless even if further research also points to an association, the risk would be small, said Dr. David Bell, an urologist with Capital Health in Halifax. "This is a very rare malignancy, seen in about one per 100,000 men per year," said Bell. "One has to really question the significance of this."