At the same time, genetic predispositions or environmental factors that increase inflammation may likewise contribute to an individual's personality. For example, experimentally raising circulating levels of IL-6 leads to increases in state negative affectivity and decreases in performance on memory tasks (Reichenberg et al. 2001). Similarly, chronic inflammation due to diseases or other causes may reduce an individual's emotional resiliency or the cognitive resources necessary to control impulsive behavior. Further, mutual feedback between personality and IL-6, as well as other inflammatory mediators, may progressively increase morbid tendencies over time. We found some evidence of this in the current study: The correlations between IL-6 and Neuroticism and Conscientiousness were stronger among the older participants in our sample. In future research, multiple assessments of personality and levels of IL-6 over time are needed to test for this potential reciprocal influence.
