A large new prospective study has reported that neither introversion nor neuroticism increase the risk of any type of cancer or reduce survival after a cancer diagnosis. It has been hypothesized that introversion and neuroticism (a tendency to worry, have anxiety, and experience emotional ups and downs) both increase the risk of cancer and that there is fact a "cancer personality." Numerous previous studies have investigated personality traits as risk and prognostic factors for cancer without establishing any clear links between personality and cancer.

The current study included data concerning 59,548 Swedish (enrolled during the period 1974 to 1999) and Finnish (1976 to 2004) adults who were initially cancer free. Participants completed a questionnaire at baseline designed to provide information for the Eysenck Personality Inventory, as well as information concerning health behavior. A total of 4,631 cancer cases were identified during a follow-up period that extended up to 30 years. To evaluate the association with cancer survival among the Finnish participants, the authors identified 2,733 Finnish cancer cases followed by 1,548 deaths during a follow-up period of up to 29 years.

Neither extraversion nor neuroticism were found to be associated with risk of cancer, regardless of the type of cancer. In addition, no significant link was found between these personality traits and the risk of death after a cancer diagnosis. The authors conclude that the data does not support the hypothesis that extraversion and neuroticism influence risk of cancer or affect survival after cancer.