Intraindividual variation in recent stress exposure as a moderator of cortisol and testosterone levels

Intraindividual variation in recent stress exposure and its impact upon cortisol and testosterone was investigated. Over 1 year, 72 young male firefighters completed the Daily Stress Inventories, for 2 shift cycles (16 days), every 3 months. At the end of each 16-day period each participant attended a 1-hr morning assessment session. Saliva samples and blood pressure measurements were taken at 10-min intervals, and at 30 min, a blood sample was drawn. Across the year of assessment, there were significant linear relationships in reported stress and in neuroendocrine activity. In contrast to expectations, as daily stress decreased across the year (p < .008), salivary cortisol increased (p < .001) and testosterone levels decreased (p < .001). Within-subjects comparisons of the sessions with the highest and lowest stress confirmed these linear relationships: Lower stress prior to the assessment session was associated with higher cortisol levels (p < .01). These results, though in contrast to the orthodoxy concerning the association between stress and cortisol, are supported by findings in a number of other studies and may constitute down regulation of cortisol activity following an increment in stress exposure. This research was supported by the Medical Research Council, United Kingdom. We are grateful to the London Fire & Civil Defence Authority for their cooperation.