Researchers dispute cancer-personality link

Q and A

April 15, 2005|By Judy Foreman | Judy Foreman,SPECIAL TO THE SUN

Is there such a thing as a cancer-prone personality?

The answer is an emphatic no, according to Swedish and Danish researchers who conducted a study that was recently published online by the journal Cancer.

The idea that some people might have an increased risk of cancer - perhaps those who are extroverted, emotionally contained or who have aggressive, Type A personalities - has been an insidious, blame-the-victim kind of notion for decades. And some studies have suggested a link between personality traits and cancer.

But the huge, new study of nearly 30,000 Swedish twins who were followed for 25 years appears to settle the issue once and for all.

The researchers studied two personality traits in particular, extroversion (a high tolerance for intense social activity) and neuroticism (high anxiety and high emotional arousal), and concluded that there is no link between these traits and cancer.

"For now, we can conclude that our results add to the evidence that personality does not contribute to the development of cancer," they wrote.

Debunking the personality-cancer hypothesis is important, said Ann Webster, a psychologist at the Mind/Body Medical Institute in Boston. "Thank heavens someone has finally discovered this," she said. "I never believed that hypothesis. I am more interested in looking at people's optimism, resilience, coping styles and willingness to make lifestyle changes."

The connection between cancer and personality has been debunked, but behavior is still important, said Dr. LaMar McGinnis, a senior medical consultant for the American Cancer Society in Atlanta. He noted that smoking, excessive drinking, lack of exercise and obesity all contribute to cancer.

My husband has brown eyes. Mine are blue. Our son's are green. How is eye color inherited?

Scientists used to think that inheritance of eye color followed simple, Mendelian rules, which held that there was a gene for brown eyes that was dominant and one for blue eyes, which was recessive.

It turns out that things are a bit more complicated. "It's not that there is a brown pigment and a blue pigment and a green pigment. There is just one pigment, melanin, and how much you have determines the color of your eyes," said Dr. Bonnie Henderson, director of the comprehensive ophthalmology service at Massachusetts Eye and Ear Infirmary.

People who are albinos, for instance, have no melanin at all, and their eyes look pink because of blood vessels in the back of the eye.

People with blue eyes have very little melanin, while people with brown eyes have a lot. People with green eyes are in between.

So far, scientists have discovered six genes for eye color, and there are undoubtedly more, said Nicholas Katsanis, an assistant professor of ophthalmology at the Institute of Genetic Medicine at Johns Hopkins Medical Institutions.

Each of these genes contributes in a different way to the "life cycle" of melanin - the amount produced and recycled within eye cells.

"Imagine a hat with different colored marbles inside," Katsanis said. "You put your hand in, get a bunch of colors. Eye color is like that. It's a combination of colors that is quasi-random but is controlled by the six genes you inherit from your mother and the six you get from your father."

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