No association between neuroticism and extroversion – and cancer

There is no association between two specific personality traits – neuroticism and extroversion – and cancer, according to a new study, one of the largest prospective twin studies to examine this issue.

The study, published in the March 1, 2005 issue of CANCER, a journal of the American Cancer Society, also finds no evidence that personality traits indirectly lead to cancer through behavioral factors, such as smoking.

Personality traits are popularly cited as risk factors for cancer. Some studies have gone so far as to suggest that two traits in particular, neuroticism and extroversion, may be such risk factors. Scientists have hypothesized that a high degree of extroversion and low degree of neuroticism are associated with an increased risk. Some studies further show that these personality traits influence known risk behaviors that would explain the increased cancer risk. However, other studies, some with larger study populations and better study designs, have found no such associations.

Pernille Hansen, M.A. of the Department of Psychosocial Cancer Research at the Institute of Cancer Epidemiology in Copenhagen, Denmark led a team of investigators who reviewed cancer history, health behavior, and personality trait data collected from 29,595 Swedish twins enrolled in the Swedish Twin Registry. These patients were born between 1926-1958 and were followed an average 25 years.

A total of 1898 instances of cancer were reported in this cohort. Analyses demonstrated no association between either neuroticism or extraversion and any group of cancer. Moreover, even after these factors were combined, no increased cancer risk was identified.

"We found no indication of an association between certain personality traits and risks for cancer," conclude the authors, "nor did we find support for an indirect association where certain personality traits influence health behavior and thus indirectly affect risk for cancer."