Cortisol Excretion During the Defense Reaction in Humans MATS FREDRIKSON, PHD, ORJAN SUNDIN, PHD, AND MARIANNE FRANKENHAEUSER, PHD Twelve subjects with specific phobias were exposed to slides with a phobic or a neutral content while cortisol excretion, electrodermal activity, and distress-ratings were studied. Six subjects fearful of blood and mutilation, and six of snakes or spiders, were presented with two sets of ten different slides (phobic or neutral; 8-sec exposures, separated by 50-sec intervals) with the order of presentation balanced between days. Before and after each session, subjects rated feelings of distress, and urine samples were obtained for the determination of cortisol by radioimmunoassay. Electrodermal activity was recorded before and during slide presentation. Compared to neutral exposures, phobic slides elicited larger cortisol excretion, higher distress ratings, and greater skin-conductance responses with slower recovery. No differences between animal and blood and mutilation phobics were observed. Thus, humans having specinc phobias exhibit pituitary-adrenal cortical arousal during the defense reaction elicited by slides of their phobic objects. Phobics confronted with their phobic object report fear and display heart-rate acceleration and skin conductance re- sponses with a slow recovery (1—5). This has been interpreted as an example of the defense reaction described by Hilton (cf. 6) and Sokolov (7) and linked to the sym- pathetic-adrenal medullary axis with in- creased excretion of epinephrine and nor- epinephrine (8). In nonphobic subjects, states of fear or anxiety have been asso- ciated with increased activity also of the pituitary-adrenal cortical axis, reflected in high cortisol levels (9). In cats (10) and monkeys (11), the defense reaction elic- ited by implanted hypothalamic electrode stimulation is accompanied by increased plasma cortisol levels. The electrodermal defense reaction is characterized by skin conductance responses with a slow recov- ery (12) that also habituate slowly. In the present study, we used half-time recovery, as described by Edelberg (12), and skin- conductance habituation rate to index the defense reaction. We asked whether the defense reaction elicited in phobics con- fronted by slides of their feared object is accompanied by elevated urinary cortisol levels. From the Psychology Division, Department of Psy- chiatry and Psychology, Karolinska Institute, and De- partment of Psychology, University of Stockholm (M.F.; M.F.) and the Department of Clinical Physi- ology, University Hospital, Uppsala, Uppsala, Swe- den (M.F.; O.S.). Address reprint requests to: Mats Fredrikson, De- partment of Psychiatry and Psychology, Karolinska Hospital, Box 60500, S-104 01 Stockholm, Sweden. Received November 4,1983; revision received Oc- tober 2, 1984. MATERIALS AND METHODS Subjects Twelve phobics were recruited by means of ad- vertisements in a local paper. Three men and three women were phobic of blood and mutilation, three women were phobic of snakes, and three woman were phobic of spiders. They were paid for their partici- Psychosomatic Medicine Vol. 47, No. 4 (July/August 1985) Copyright © 1985 by the American Psychosomatic Society, Inc. Published by Elsevier Science Publishing Co., Inc 52 Vanderbllt Ave., New York, NY 10017 313 0033-3174/8553.30