Personality Doesn't Affect Cancer Risk
No Link Seen in Large, Long-Term European Study
Jan. 24, 2005 -- Personality traits don't increase cancer risk, say Danish researchers in the March 1 edition of the journal Cancer.
Pernille Envold Hansen, MA, and colleagues studied nearly 30,000 Swedish twins, following them for 25 years. The twins had enrolled in the Swedish Twin Registry when they were 15-48 years old.
Back in 1973, the twins had taken an 18-item personality questionnaire. The survey gauged neuroticism and extroversion, two traits that have drawn speculation about cancer risk.
The researchers also accessed the Swedish Cancer Registry, which covers the entire Swedish population. In Sweden, pathologists are required to report tumors, and virtually all cancers (98%) are verified.
During the study, the twins had a total of 1,898 cancers.
Personality Not a Factor
The data showed no connection between the development of cancer and neuroticism or extroversion.
Neuroticism is associated with emotional arousal. Highly neurotic people tend to be more worried, anxious, and emotionally unstable than others.
But neuroticism apparently has nothing to do with cancer, the researchers say. They found no evidence linking low neuroticism to any type of cancer.
No Extra Cancer Risk for Extroverts
The study also found no ties between cancer and another personality trait -- extroversion.
"Extroverts tend to have a nervous system that quickly inhibits excess stimulation," the researchers explain. That makes intense social activity tolerable -- and sometimes even desirable -- for extroverts.
Extroverts were not more likely to get cancer, say the researchers.
What's more, extroversion and neuroticism weren't associated with behaviors that increase cancer risk. For instance, extroverts and people with low neuroticism weren't especially likely to smoke.
The researchers took into account alcohol intake, exercise, diet, body mass index (BMI), oral contraceptives, and education. Personality didn't sway any of those factors toward cancer risk.
Other studies have suggested that personality affects cancer risk. But some of that work is flawed, say the researchers. They note that "well-conducted" studies on cancer and other personality traits are in line with their findings.
For instance, the researchers note that a 20-year study of more than 11,000 women showed no link between type A behavior and breast cancer. Type A behavior was defined as time urgency, ambitiousness, competitive drive, and aggressiveness.
Likewise, other studies have shown that hostility and psychological vulnerability don't affect cancer risk, say the researchers.
It's possible that personality and high life stress could interact to influence cancer risk, they say. But so far, that hasn't been verified.