Interindividual differences in the susceptibility of the cortisol system: an important factor for the degree of hypercortisolism in stress situations?

Whereas in psychophysiological research, the specificity of the individual responses has been assumed to be an important trait variable influencing the investigated parameters in stress experiments or in psychopathological states, in psychoneuroendocrinology, the individual differences in the susceptibility of the investigated neuroendocrine axes have been widely neglected. The present study on the cortisol response of 12 healthy young men to 5 different stress tests is considered to be an initial orientation step into this field. All five stress tests (quiz, arithmetic tasks, stress film, cold pressor test, and physical exercise test) could be proven to be effective stimuli regarding the cortisol system. There was, however, a broad spectrum of cortisol responses among the 12 subjects, with a continuum between complete reactors and nonreactors. This did not correlate with the subjective judgment of stress at all. Although the data showed a tendency toward an augmented dispersion of the response frequencies in comparison with random variation, the limited sample size of subjects and stress tests did not allow a statistically significant proof of a stimulus-independent, individual response specificity. Further experimental clarification seems to be necessary to avoid misinterpretations of neuroendocrine data in psychiatric disorders due to neglect of this variable.