Are neuroticism and extraversion related to morning cortisol release in healthy older people?

The cortisol awakening response (CAR) is a discrete component of the hypothalamic-pituitary-adrenal axis (HPA-axis) function that has been widely related to both health and some personality traits. There is evidence that neuroticism and extraversion affect health and well-being and play a damaging or protective role, respectively. In this study, we aimed to explore the relationship between these personality dimensions and morning cortisol concentrations in people aged 55 or older. To do so, morning saliva samples were collected on two consecutive weekdays from a total of 160 older men and women. Neuroticism and extraversion were assessed using the Eysenck Personality Questionnaire-Revised, short form (EPQ-RS). Our results showed that neuroticism was negatively related to overall morning cortisol concentrations (AUCG) (i.e., area under the curve with respect to the ground in cortisol levels), but not to the CAR. When we explored sex as a moderator, neuroticism was related to a CAR of increased magnitude in women, although this relationship was not significant in men. No significant relationships were found between extraversion and CAR or AUCG, regardless of sex. In conclusion, neuroticism - but not extraversion - was related to HPA-axis function in older adults, highlighting its potential relevance in health alterations associated with HPA-axis functioning.