Danish researchers have concluded that, on its own, personality is not a risk factor for cancer, although it may be linked to behaviors -- like smoking, for example -- that are linked with an increased risk.
Previously, investigators have found links between psychic vulnerability and other physical symptoms and diseases such as pain, irritable bowel syndrome and peptic ulcer disease. Studies have also suggested that such specific personality traits as depression and repression are associated with an increased risk of developing cancer.
The study, which appears in the June 15 issue of Cancer, is the first to look at the link between "psychic vulnerability" and cancer.
And experts say the findings should reduce people's stress over whether stress causes cancer.
"I think it's a fairly widespread belief that stress causes illness of all sorts, and, in particular, cancer. But there's really not a shred of evidence, and this study helps to put this issue in a more proper scientific framework," Dr. Jeffrey Weitzel, director of clinical cancer genetics at the City of Hope Cancer Center in Los Angeles, says.
Two competing theories seek to explain the apparent connections between cancer and personality traits. One posits that personality leads to behaviors (like smoking) that influence the risk of cancer. Another theory says there's a common underlying biological factor, which impacts both personality and the risk for cancer.
In this study, the researchers used the "Test of Psychic Vulnerability," originally developed to identify men who were not psychologically fit for military service, to test for a cancer association.
The exact meaning of the term is somewhat elusive. "You cannot say it's clearly neurotic, but a little bit insecure," says the lead author of the study, Dr. Christoffer Johansen, head of the psychosocial cancer research department at the Danish Institute of Cancer Epidemiology.
People who have psychic vulnerability, he adds, are "not so good in social relations and have problems obtaining friendship. It's a kind of a social-psychological mismatch with the average population."
"The researchers looked at various psychological conditions that are probably fairly widespread, and the good news is that they did not find an association," Weitzel says. "It's a reasonable scientific study, especially from a psycho-epidemiologic perspective."
The study looked at data, including demographic and health questionnaires as well as the Test of Psychic Vulnerability, from 5,136 people living in Copenhagen County in Denmark. This information was then cross-referenced with the Danish Cancer Registry to find associations between cancer and personality, age, alcohol consumption, smoking, social class, marital status or body mass index.
Even after adjusting for various known cancer risk factors, the investigators did not see an increased risk for cancer in relation to psychic vulnerability. Not surprisingly, however, older people had an increased risk, as did those who smoked and those who drank more than 14 units of alcohol a week.
Very often, cancer patients point to a stressful event in their life and feel it has a causative effect on their illness, says Ruth Oratz, an associate professor of clinical medicine at New York University School of Medicine, who also emphasizes that there is no evidence for this point of view.
"It's not that there's no link between our emotional state and physical health, it's just that that link is probably not a strong direct link," she says.
But there may be an indirect link, and these findings buttress the hypothesis that personality traits lead to behaviors (smoking and drinking alcohol included), that, in turn, translate into an increased risk for cancer.
"We didn't find an increased risk of cancer, but what is interesting is that there was an increased number of smoking- and alcohol-associated cancers in psychically vulnerable individuals," says Johansen.
The conclusions also suggest where to aim future prevention efforts. "It shows a new theme for prevention of smoking," Johansen says.
Another paper by the same authors, this one appearing in this week's American Journal of Epidemiology, linked 90,000 depressed individuals with an elevated cancer risk and an increased risk of smoking.
"This points to the fact that more of the smoking prevention activities should be aimed at people who are depressed and who demonstrate psychic vulnerability," Johansen says.
And for cancer prevention in general, it comes back to the same old story: Eat a balanced diet with lots of green leafy vegetables, cut out tobacco and drink alcohol only in moderation, advises Weitzel.
What To Do