Low cortisol and a flattening of expected daytime rhythm: Potential indices of risk in humandevelopment

Abstract

Since the work of Hans Selye, stress has been associated with increased activity of thelimbic–hypothalamic– pituitary–adrenocortical (LHPA) axis. Recently, anumber of studies in adults have shown that this neuroendocrine axis may be hyporesponsive in anumber of stress-related states. Termed hypocortisolism, the paradoxical suppression of theLHPA axis under conditions of trauma and prolonged stress presently challenges basic concepts instress research. Adverse conditions that produce elevated cortisol levels early in life arehypothesized to contribute to the development of hypocortisolism in adulthood. However, asreviewed in this paper, hypocortisolism also may be a common phenomenon early in humanchildhood. Although preliminary at this point, the ubiquity of these findings is striking. We arguethat developmental studies are needed that help explicate the origins of low cortisol and todetermine whether the development of hypocortisolism is, in fact, preceded by periods of frequentor chronic activation of the LHPA axis. We also argue that developmental researchers whoincorporate measures of salivary cortisol into their studies of at-risk populations need to be awareof the hypocortisolism phenomenon. Lower than expected cortisol values should not necessarilybe relegated to the file drawer because they contradict the central dogma that stress must beassociated with elevations in cortisol. Lastly, we note that evidence of low cortisol under adverseearly life conditions in humans adds to the importance of understanding the implications ofhypocortisolism for health and development.