Five-factor model personality traits and 24-h urinary cortisol in the Baltimore Longitudinal Study of Aging.

Stress is implicated in models of personality and health as a mechanism that explains why traits like conscientiousness and neuroticism are associated with long-term health outcomes. Evidence for an association between personality and cortisol, a biological marker of stress, however, has been inconsistent. This study examined the association between Five-Factor Model personality traits and 24-h urinary cortisol (operationalised as a ratio of urinary free cortisol to creatinine) measured up to 12 times over intervals as long as 30 years in the Baltimore Longitudinal Study of Aging (Mage  = 61.21, SD = 15.46; 49% female). There was a modest association between conscientiousness and lower mean-level cortisol that was attenuated only slightly in the fully-adjusted model. Neuroticism and the other traits were unrelated to cortisol levels, and none of the traits was related to cortisol change over time. The null association for neuroticism suggests that its relation with long-term health may be primarily through pathways other than cortisol. The modest association between conscientiousness and 24-h urinary cortisol replicates a previous finding with a longer-term measure of cortisol measured from hair, which calls for more research on the robustness and replicability of this finding. Cortisol may be one pathway through which conscientiousness is associated with health outcomes.