Feb. 8, 2013 -- Stress on the job may cause a lot of things, but at least you can rest safe knowing that cancer isn't likely one of them.
A new study finds that overall, high job stress was unlikely to be an important risk factor for colorectal, lung, breast, or prostate cancers. It was also not associated with an overall risk of cancer.
About 90% of cancers have been linked to causes such as environment and lifestyle. Evidence for other factors, including psychological and social ones, remains tentative.
The researchers from the Finnish Institute of Occupational Health, Helsinki, wanted to know if stress might play a role.
Stress has been linked with a body response that causes extra stress hormones, they write. These hormones are able to both trigger and maintain chronic inflammation, which has been shown to play a part in cancer.
Work and work-related factors are important sources of stress for many working people, says Katriina Heikkilä, PhD, and lead researcher. She says work can also help well-being.
The study used a measure of work-stress called job strain, defined as high demands and low control over work. Heikkilä says the study found this measure was not associated with cancer risk.
Still, "it is not known how long a person needs to be exposed to stress for it to be harmful to health, but one would think that longer exposure would be worse than shorter," she says.
"In our study, work-related stress was measured at one point in time, and thus some of the participants had been exposed to stress for longer than others," Heikkilä says. "It would be interesting to look into this in future studies -- whether the duration of the stress exposure is relevant to the risk of cancer or other diseases."
Heikkilä and her colleagues looked at 12 studies conducted between 1985 and 2008 in Finland, France, the Netherlands, Sweden, Denmark, and the United Kingdom. More than 116, 000 people were involved.
The researchers took into account job strain, age, sex, socioeconomic position, body mass index, smoking, alcohol intake, and whether they developed cancer.
Of these people, almost 5,800, or 5%, developed some type of cancer over a 12-year period.
Heikkilä says it may be that work-related stress alone is not enough to contribute to cancer development. It may be that a combination of several stressful factors, such as stress from negative life events or caregiver stress, is needed.
"It is also possible that stress -- at work or elsewhere -- is related to the risk of some rarer types of cancer, which we did not investigate in our study," says Heikkilä.
The research is published online in the BMJ.