Being open and easy-going can win you friends, and it probably won’t raise your cancer risk either, according to a study published Monday.

The findings, from a long-running study of nearly 30,000 Swedish twins, add to research refuting the notion that there are certain cancer-prone personalities.

In this case, the investigators found no association between cancer risk and either of two personality traits: extroversion, the tendency to be friendly and outgoing; and neuroticism, a proclivity toward worry, anxiety and emotional ups and downs.

Some past research has found that these two realms of personality may sway cancer risk. One theory is that people who are highly outgoing or consistently calm may have a heightened risk of cancer - particularly those with both traits. Their extroversion, the idea goes, may make them seek out stimulation and potentially stressful situations, while their coolness may deny them an emotional outlet for the stress.

But some of those studies have suffered from weaknesses such as not accounting for health behaviors, like smoking, or taking measures of personality after - not before - people develop cancer, according to the new study’s lead author, Pernille Envold Hansen, a psychologist at the Danish Cancer Society in Copenhagen.

“The results from the current study show that there is no association between certain personality traits and risk for cancer,” Hansen told Reuters Health, noting that the findings are in line with those from several recent, well-designed studies.

The study, published online by the journal Cancer, included nearly 30,000 Swedish twins born between 1926 and 1958. The participants completed a standard survey on personality traits and lifestyle habits in 1973, and subsequent cancer deaths were recorded through 1999.

Hansen’s team found no clear relationship between the risk of any type of cancer and a person’s level of neuroticism or extroversion. Nor did they find that the two traits were important in health behaviors such as smoking.

The study did have limits, the researchers note, including a one-time measurement of personality traits. Indeed, they add, the study of personality and cancer risk in general reflects an “assumption that individuals have certain characteristics that are more or less stable across time and space.”

“It’s still conceivable,” Hansen said, “that personality could play a role in cancer risk - for example, by affecting how we handle stress.”

As for whether personality traits other than extroversion or neuroticism could be involved in cancer risk, Hansen noted that research on several other dimensions of personality has yet to be convincing. These include the “type A” personality - the classic go-getter who is ambitious, aggressive and competitive - and the “type C” personality, which describes people who are submissive and hold in negative emotions.

SOURCE: Cancer, online January 24, 2005.