Smoking is a risk factor for lung cancer, and this knows everybody. But only some people know that men who frequently smoke can have a higher risk of testicular cancer than those who don’t smoke, according to a new study. But this "hypothesis" needs to be more tested because not all the people believe in it.

A man’s lifetime chance of developing this disease is about 1 in 300 but dying of it is about 1 in 5000, which is means that testicular cancer is relatively rare. Also researchers found that even frequent or long-term marijuana smokers could have about double the risk of testicular cancer than non-smokers.

In the study, a team led by Janet R. Daling, MD of the Fred Hutchinson Cancer Research Center in Seattle, Washington, interviewed 369 men between the ages of 18 and 44 years old from the Seattle-Puget Sound area who had been diagnosed with testicular cancer. They compared those men to 979 men who lived in the same area, but did not have cancer.

At the end of the investigation researchers found that 26% of the testicular cancer patients were smokers at the time of diagnosis, compared with 20% of men without cancer. But marijuana users had 2.3 times the risk of a type of testicular cancer known as a nonseminoma as those who were not.

Testicular cancer is divided into two types, pure seminomas (60% of cases) and nonseminomas (40% of cases.) The link was much weaker in men with seminomas. Many scientists believe that most cases of testicular cancer actually get their start in early fetal life. Having an undescended testicle, a relatively common birth defect and is a key risk factor for the disease.

Still, the results are considered preliminary and need to be confirmed with more research.