Long periods of stress appear to raise the cancer risk in men by 20 percent compared with those who say they’re stress-free, according to a survey by a Japanese research team.

The research was conducted between 1990 and 2012 and tracked 79,301 men and women between 40 and 69.

The team, which included members of the National Cancer Center, asked the subjects about their perceived stress levels on two occasions — once at the beginning of the survey and five years later.

The cancer risk for men who replied on both occasions that they had a lot of stress proved 19 percent higher than for those who said they didn’t on both occasions.

For men who replied they had little or moderate stress at the start of the survey but a lot of stress five years later, the risk was 20 percent higher than men who reported no stress on both occasions.

Of those polled, 12,486 developed cancer. The team said that stress particularly increased the risk of liver and prostate cancer.