A Review of Psychoendocrine Research on the Sympathetic-Adrenal Medullary System

There appears now to be no reasonable doubt that both epinephrine and norepinephrine belong to the category of hormones which are responsive to psychological influences. Catecholamine levels, furthermore, appear sensitively to reflect relatively common, psychological reactions associated with “everyday” events, tasks, and activities. As in the case of the pituitary-adrenal cortical system, it appears that the central nervous system may exert an ongoing “tonicity” on catecholamine levels which reflects environmental and psychological factors. The findings in this field have, in fact, suggested that systematic study of a wide variety of common tasks or activities and common methods of relaxation may reveal a surprisingly extensive range of diverse, ongoing psychoendocrine adjustments in everyday life. The possibility that catecholamine responses to such events may further be correlated with performance effectiveness, as suggested by some studies, may be another fruitful area for future exploration. These approaches appear likely to have industrial and military, as well as physiological and medical, implications. There is some evidence that psychological factors may lower as well as raise catecholamine excretion levels and that certain types of pleasant as well as unpleasant forms of emotional reaction may be associated with elevated catecholamine levels. Dissociation between epinephrine and norepinephrine levels in relation to psychological influences has been demonstrated. The precise psychological determinants of epinephrine versus norepinephrine release remain one of the most intriguing issues in the psychoendocrine field. While there are some indications, particularly in human studies, that aggressive versus anxious reactions are particularly relevant to the catecholamine excretion pattern, this problem is in need of further, more comprehensive study. Funkenstein's concept of the psychological basis of differential catecholamine secretion cannot yet be regarded as being definitively evaluated. It appears that anticipation of experiences or situations involving a high degree of novelty or unpredictability may be associated with especially marked catecholamine responses. Marked individual differences in catecholamine and psychological responses to a given situation have been found in many studies. The significance of mean group values based solely upon situational criteria is therefore rather limited. Increasing emphasis should be placed in the future on defining the psychological, constitutional, physical or other determinants of these differences in levels of response between individual subjects. From the psychological standpoint, this will require systematic assessment of multiple factors, including emotional state, the style and effectiveness of psychological defenses, dynamic factors in each individual's behavior, and cognizance of the social environment. Many of the methodological principles which have emerged from psychoendocrine studies of the pituitary-adrenal cortical system83 also have been found to apply to the study of epinephrine and norepinephrine regulation. These principles pertain to such issues as the choice of reliable hormone assay methods, fitting the sample collection design to the dynamics of the response under study, taking the diurnal rhythm fully into account in acute experiments, the choice of control measures (e.g., eliminating novelty or “first experience” effects from clinical studies), the value of “longitudinal” versus “contrast” studies in patients, and the choice of methods for obtaining correlative psychological data.83 Lack of systematic psychological measurements has been one of the principle deficiencies in psychoendocrine research on the sympathetic-adrenal medullary system. There has been a strong emphasis in this field so far on the study of normal human subjects in stressful laboratory situations. In comparison with research on the pituitary-adrenal cortical system, 83 catecholamine studies are not yet so well balanced in terms of studies of psychiatric disorders in patients, of normal human subjects in natural life situations, and of highly controlled stressful laboratory conditions with experimental animals. There has also been a notable lack of studies of catecholamine levels in relation to chronic stressful situations that extend over periods of weeks, months, or years, similar to work concerned with 17-OHCS levels.83 As in the case of the pituitary-adrenal cortical field, the findings reviewed here indicate an urgent need to incorporate the psychoendocrine aspect of sympathetic-adrenal medullary regulation more broadly into attitudes concerning physiology--particularly from the practical viewpoint in work involving metabolic or endocrine measurements in conscious animal or human subjects. Much of our existing knowledge of the response of this system to physical stimuli, which has been gained by work in conscious subjects, may bear close re-evaluation with regard to the possible role that psychological factors may have played in the determination of the observed catecholamine responses. The findings in this field reinforce the conclusion that psychoendocrine research and concepts must not remain confined to the psychiatric and behavioral fields alone, but rather that they have important implications for future work in other biological fields as well.