Lifetime adversity leads to blunted stress axis reactivity: studies from the Oklahoma Family Health Patterns Project.

BACKGROUND: Can stressful events in early life alter the response characteristics of the human stress axis? Individual differences in stress reactivity are considered potentially important in long-term health and disease; however, little is known about the sources of these individual differences. We present evidence that adverse experience in childhood and adolescence can alter core components of the stress axis, including cortisol and heart rate reactivity.
METHODS: We exposed 354 healthy young adults (196 women) to public speaking and mental arithmetic stressors in the laboratory. Stress responses were indexed by self-report, heart rate, and cortisol levels relative to measures on a nonstress control day. Subjects were grouped into those who had experienced 0, 1, or 2 or more significant adverse life events, including Physical or Sexual Adversity (mugged, threatened with a weapon, experienced a break-in or robbery or raped or sexually assaulted by a relative or nonrelative) or Emotional Adversity (separation from biological mother or father for at least 6 months before age 15).
RESULTS: Experience of adversity predicted smaller heart rate and cortisol responses to the stressors in a dose-dependent fashion (0 > 1 > 2 or more events) (F values = 5.79 and 8.11, p values < .004) for both men and women. This was not explained by differences in socioeconomic status, the underlying cortisol diurnal cycle, or subjective experience during the stress procedure.
CONCLUSIONS: The results indicate a long-term impact of stressful life experience on the reactivity of the human stress axis.