Elsevier

Psychoneuroendocrinology

Volume 30, Issue 10, November 2005, Pages 939-946
Psychoneuroendocrinology

Developmental determinants of sensitivity and resistance to stress

https://doi.org/10.1016/j.psyneuen.2005.03.013Get rights and content

Summary

The purpose of this paper is two fold. First, to revisit the issue of the definition of stress and to highlight the difficulties with the contemporary definitions and, second, to review the literature on the influence of early experiences on the endocrine stress responses and behavior in rodents, sub-human primates and humans. Early experiences, usually involving some manipulation that results in disruption of the mother–infant relationship, have been shown to have long-term influences on the behavioral and endocrine responses to stress. In the rodent, brief periods of separation result in an attenuated adrenal response to stress (reduced secretion of corticosterone). In contrast, longer periods of separation result in an exaggerated response and several behavioral anomalies i.e. increased alcohol consumption, increased startle response etc. However, the effects of disruptions of the mother–infant relationships in primates reveal a pattern of behavioral disturbance but little influence on the endocrine response. Brief maternal separations result in a blunted cortisol response in juvenile squirrel monkeys. The long-term effects of early experiences in humans are very difficult to interpret. It is not possible to determine the length and severity of the experiences, and when in development the experiences were imposed on the child. Despite these limitations, there is a general consensus that adverse early experiences contribute to adult psychopathology.

Section snippets

Defining stress

This symposium was organized to honor Prof Holger Ursin. His distinguished career has covered a broad spectrum of studies ranging from basic neuroanatomy to complex issues related to behavioral medicine. My association with Prof Ursin has been primarily through his research on the psychobiology of stress. After the completion of our last effort to define stress (Levine and Ursin, 1991), I made myself the promise that I would never again engage in what I consider a futile exercise. One of the

Rodent early experiences

What has been obvious throughout the history of research on the HPA responses to stress is that stress is indeed in eyes of the beholder. In all my years of measuring the so-called stress hormones, I have never been able to eliminate the error bars. Depending upon the species, the type of stress, the genetic background etc. the error bar can be reduced but never eliminated. Plotsky et al. (1998) have attempted to model the complex set of interactions that occur both developmentally and in

Primates

For most infant primates, the relationship with the mother is the single most important feature of the infant's environment. In addition to the nurturing aspects of the mother–infant (M–I) relationship, the mother also has the capacity to buffer the infant's stress responses and thus provides a secure base that permits the infant to explore the environment. The power of this relationship is clearly manifested when the infant is acutely separated from the mother. The infant emits high levels of

Human

The available studies that have examined the effects of early adverse experience in humans are not extensive. However, due to availability of assays that permit cortisol to be measured in saliva (Kirschbaum and Hellhammer, 1994), which provide a relatively easy and non invasive technique for obtaining repeated samples, there are now more human studies that have examined the long-term effects of early experiences on stress reactivity in adulthood. These studies all indicate that early adverse

Conclusion

The prevailing view that early experience has pervasive and profound effects on the adult responses to stress has been well documented in several species. In this review we have presented data obtained in rodents, non-human primates and humans that all indicate that the quality of early life events can influence the neural circuits that regulate the stress response. It is important to note that there are considerable differences between species. In the rodent, both behavioral and endocrine

Acknowledgements

This research was supported by Grants HD 0281 from the National Institute of Child Health and Human Development and Grant MH-45006 for the National Institute of Mental Health. I wish to express my gratitude to the Post doctoral fellows, graduate and undergraduate students whose efforts have made much of this work possible.

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