Personality nuances and inflammation: A coordinated analysis of six samples

Five-Factor personality domains are associated with inflammatory markers across adulthood. Personality nuances, the most specific personality characteristics at the bottom of the personality hierarchy that are typically measured by individual questionnaire items, may provide more information on which specific characteristics of traits are related to inflammation. Using six cohort studies (total N > 19,000, age range: 25-104 years) that measured nuances using items from the Midlife Development Inventory (MIDI), this study examined the association between personality nuances and two inflammatory markers: c-reactive protein (CRP) and interleukin-6 (IL-6). Across most samples and a meta-analysis, the extraversion item lively and the conscientiousness items organized and hardworking were related to lower levels of CRP and IL-6. The extraversion item active was the strongest item-level correlate of lower CRP in the meta-analysis and across most samples. Domain-level analyses indicated that higher conscientiousness was associated with lower CRP and IL-6, whereas higher extraversion was associated with lower CRP. Neuroticism, openness, and agreeableness domains and items were mostly unrelated to inflammatory markers. The associations between the items active and hardworking and inflammatory markers persisted in most samples controlling for their respective extraversion and conscientiousness domains. Item-level analyses provide more detailed insights into the specific personality nuances connected to inflammation, showing that the active component of extraversion, rather than components related to sociability, are associated with inflammation.