Biological Sensitivity to Context

Conventional views suggest that exaggerated biological reactivity to stress is a harmful vestige of an evolutionary past in which threats to survival were more prevalent and severe. Recent evidence, however, indicates that effects of high reactivity on behavior and health are bivalent rather than univalent in character, exerting both risk-augmenting and risk-protective effects depending on the context. These observations suggest that heightened stress reactivity may reflect increased biological sensitivity to context, with potential for negative health effects under conditions of adversity and for positive effects under conditions of support. From an evolutionary perspective, the developmental plasticity of the stress-response systems, along with their structured, context-dependent effects, suggests that variation in these systems has been adaptively patterned to increase the capacity of children to match their stress-response profiles to anticipated developmental environments. Taken together, these theoretical perspectives generate a novel hypothesis: that there is a curvilinear, U-shaped relation between early exposures to adversity and the development of stress-reactive profiles, with high-reactivity phenotypes disproportionately emerging within both highly stressful and highly protected early social environments.