"Cortisol helps us respond to stressful experiences and do something about them," she said. "It is necessary for survival -- fluctuations in this hormone assist us in meeting the changing demands we face in our daily lives."
The first of its type, the study shows that it is not just on average that people who have more negative emotions have higher levels of cortisol. Rather, with its detailed and intricate methodology, the study shows a sensitive day-to-day dance between experience and cortisol. Experience influences stress hormones, and stress hormones influence experience, the study shows.
"Cortisol responds to and interacts with our daily experiences in subtle and important ways," Adam concluded.
Cortisol levels are generally high immediately upon waking, increase in the first 30 minutes after waking and then decline to low values at bedtime.
Adam, with her colleagues John T. Cacioppo and Louise C. Hawkley at the University of Chicago, and Brigitte M. Kudielka from the University of Trier, Germany, showed that changes in this pattern from one day to the next are closely interwoven with changes in our daily experiences.
The study, based on data from the Chicago Health, Aging, and Social Relations Study (CHASRS) at the University of Chicago includes 156 older adults living in Cook County who were born between 1935 and 1952 and represent a range of socioeconomic classes. Their cortisol levels were measured from small samples of saliva provided three times a day for three consecutive days. Study participants reported their feelings each night in a diary, and researchers looked at whether cortisol levels on a particular day were predicted by experiences the day before or were predictive of experiences that same day.
In addition to noting that loneliness the night before predicted higher cortisol the next morning, Adam and colleagues found that people who experience anger throughout