Early Stressful Events Can Impact Stress Response for Life, Including Cortisol Levels
This is an important question because the response of the stress axis can influence long-term health and the development of disease. Understanding the individual differences in how people respond to and are affected by stress (the differences in their stress reactivity) could be key in understanding the role stress plays in long-term health.
The study was published in the February 2012 edition of Biological Psychiatry; the article was “Lifetime adversity leads to blunted stress axis reactivity: studies from the Oklahoma family health patterns project.”
In the study, there were 354 healthy young adults; 196 of them were women. They were grouped by those who had gone through 0, 1, or 2+ significant stressful/adverse life events.These included physical or sexual events (eg, mugging, threatened with a weapon, raped, lived through a break-in, sexually assaulted by a relative). Emotional adverse events were also considered, including separation from biological parent for at least 6 months before age 15.
The researchers exposed them to certain stressors in the laboratory: public speaking and mental arithmetic.
The subjects’ stress responses were indexed by:
- heart rate
- cortisol levels relative to measurements taken on a non-stress control day
The results showed that experiencing an adverse physical, sexual, or emotional event was a predictor of a smaller heart rate and lower cortisol response in regards to the lab-induced stressors. This was seen in a dose-dependent fashion (0 > 1 > 2+ events) (F values=5.79 and 8.11, p-values < .004), and it was seen in both women and men.
This smaller heart rate and lower cortisol response could not be explained by socioeconomic differences, the subjects’ underlying cortisol diurnal cycle, or the subjects’ subjective experience in the lab during the experiment.
The study seems to show that an adverse life experience has a long-term influence on the reactivity of the stress axis, including cortisol levels.