The Dual Impact of Early and Concurrent Life Stress on Adults' Diurnal Cortisol Patterns: A Prospective Study.

Major life stress often produces a flat diurnal cortisol slope, an indicator of potential long-term health problems. Exposure to stress early in childhood or the accumulation of stress across the life span may be responsible for this pattern. However, the relative impact of life stress at different life stages on diurnal cortisol is unknown. Using a longitudinal sample of adults followed from birth, we examined three models of the effect of stress exposure on diurnal cortisol: the cumulative model, the biological-embedding model, and the sensitization model. As its name implies, the cumulative model focuses on cumulative life stress. In contrast, the biological-embedding model implicates early childhood stress, and the sensitization model posits that current life stress interacts with early life stress to produce flat diurnal cortisol slopes. Our analyses are consistent with the sensitization model, as they indicate that the combination of high stress exposure early in life and high current stress predict flat diurnal cortisol slopes. These novel findings advance understanding of diurnal cortisol patterns and point to avenues for intervention.