Study: No Evidence of "Breast Cancer Personality" (dateline October 22, 2002)

As far back as ancient Rome, people have suggested that personality can affect health. In the twentieth century, there was talk that women with so-called type A personalities—competitive, aggressive, extroverts—may be more likely to develop breast cancer than their peers. However, a large Finnish study finds no evidence to support the link between personality and breast cancer. The researchers believe their findings should reassure women who may believe in this idea and to focus on more established risk factors for the disease.

Breast cancer is the second leading cause of cancer deaths in women today (after lung cancer) and is the most common cancer among women, excluding non-melanoma skin cancers. According to the World Health Organization, more than 1.2 million people will be diagnosed with breast cancer this year worldwide.

While several factors have been identified that put women at higher-than-average risk for breast cancer, approximately 80% of women who develop the disease have no known risk factors. This has led to the idea that perhaps a woman’s personality influences her likelihood of developing breast cancer. In particular, it has been suggested that women who are aggressive, ambitious, competitive, or hostile (easily irritated or angered) may face a greater risk of developing breast cancer than more subdued, easy-going, or introverted women.

Though the "personality theory" has been refuted by physicians for years, up until now there has been limited data to negate the influence of personality on breast cancer risk. Therefore, Kirsi Lillberg of the Department of Public Health at the University of Helsinki in Finland and her colleagues followed 12,499 Finnish women aged 18 or older from 1976 to 1996. During this time, the women completed personality questionnaires.

The researchers wanted to determine whether there was a connection between the women’s responses to the personality questionnaires and their likelihood of developing breast cancer. During the period, Lillberg and colleagues identified 253 breast cancer cases among the study participants.

The analysis found no link between an extroverted personality and breast cancer risk. Women who had any assertive personality characteristics, alone or in combination, were no more likely than introverted women to develop breast cancer. In their paper in the International Journal of Cancer, Lillberg and her colleagues also cite several small studies that produced similar results.

Lillberg and her colleagues believe their study provides evidence that personality does not play an important role in breast cancer risk. Research has also failed to find significant evidence of an association between depression or stress and breast cancer risk. Instead, several other risk factors have been identified to affect the likelihood of breast cancer development. These factors include:

• Advancing age
• Family or personality history of breast cancer
• Genetic mutations of certain genes (such as BRCA1 or BRCA2)
• Early onset of menstruation or late menopause
• Never having children or having a first child after age 30
• Long-term use of hormone replacement therapy (over five years)

However, since the majority of women who develop breast cancer have no identifiable risk factors, it is likely that theories such as the "breast cancer personality" will continue to surface until they can be refuted by science.

Additional Resources and References

• The study, "Personality Characteristics and the Risk of Breast Cancer: A Prospective Cohort Study," is published in the July 2002 issue of the International Journal of Cancer, http://www.interscience.wiley.com/jpages/0020-7136/
• The August 2, 2002 Reuters Health report is entitled, "Grouchy? Type A? It Won't Affect Breast Cancer Risk," http://www.reutershealth.com/
• To learn more about risk factors for breast cancer, please visit http://www.imaginis.com/breasthealth/bc_risks.asp