Personality and immune system reactivity.

Vedhara et al. have examined the expression of inflammatory genes in 121 people who also took personality tests that rated the generally identified five major dimensions of human personality (Neuroticism, Extraversion, Openness to Experience, Agreeableness, and Conscientiousness). From the author's introduction:

...we hypothesized that pro-inflammatory gene expression would be up-regulated in extraverts and people with high levels of openness to experience (both of whom would be expected to experience elevated risk of injury/infection) and down-regulated in conscientious individuals with comparatively strong behavioural immune responses.

This is in fact what they found. From their discussion:

The present results identified systematic differences in leukocyte gene expression that correlate with individual differences on two major dimensions of human personality: Extraversion and Conscientiousness. Consistent with predictions from behavioural immune response theory, Extraversion was associated with up-regulated expression of pro-inflammatory genes, whereas Conscientiousness was associated with down-regulated expression of pro-inflammatory genes. These effects were independent of major health behavioural factors (BMI, smoking, alcohol consumption, physical activity); independent of variations in leukocyte subset prevalence; independent of negative affect; independent of minor physical symptoms and related medications; and independent of demographic characteristics as well as other major dimensions of human personality. In contrast, none of the major personality dimensions was significantly associated with differential expression of the other primary gene module involved in the CTRA profile – antiviral and antibody-related transcripts. In the context of previous data linking Extraversion and Conscientiousness to health and longevity, the present functional genomics findings may provide new insights into the molecular basis for such relationships.

Their results do not support the model of neuroticism and negative affect generating a 'disease-prone personality.' Numerous other studies have correlated the trait of conscientiousness with longevity.