Associations between dispositional optimism and diurnal cortisol in a community sample: when stress is perceived as higher than normal.

OBJECTIVES: This study examined whether dispositional optimism would be associated with reduced levels of cortisol secretion among individuals who perceive stress levels that are either higher than their normal average (i.e., within-person associations) or higher than the stress levels of other individuals (i.e., between-person associations).
METHODS: Stress perceptions and four indicators of diurnal cortisol (area-under-the-curve, awakening, afternoon/evening, and cortisol awakening response [CAR] levels) were assessed on 12 different days over 6 years in a sample of 135 community-dwelling older adults.
RESULTS: Hierarchical linear models showed that although pessimists secreted relatively elevated area-under-the-curve, awakening, and afternoon/evening levels of cortisol (but not CAR) on days they perceived stress levels that were higher than their normal average, optimists were protected from these stress-related elevations in cortisol. However, when absolute stress levels were compared across participants, there was only a significant effect for predicting CAR (but not the other cortisol measures), indicating that optimism was associated particularly strongly with a reduced CAR among participants who experienced high levels of stress.
CONCLUSIONS: Dispositional optimism can buffer the association between stress perceptions and elevated levels of diurnal cortisol when individuals perceive higher-than-normal levels of stress, and it may predict a reduced CAR among individuals who generally perceive high stress levels. Research should examine relative, in addition to absolute, levels of stress to identify the personality factors that help individuals adjust to psychological perceptions of stress.