When phobics are exposed to what they fear--be it spiders or public speaking--they experience a surge in stress hormones known as glucocorticoids. These compounds help prepare the body for action, whether fight or flight. Now researchers have found that further raising levels of the stress hormones in the body can actually reduce a phobic's anxiety.

Dominique de Quervain and his colleagues at the University of Zurich in Switzerland recruited 40 men who suffered from a fear of public speaking. In a double-blind study, the men received either a 25-milligram tablet of the glucocorticoid cortisone or a placebo. They digested the pills for an hour and then received a note informing them that they had 10 minutes to prepare a five-minute speech on why they should be hired for a job. They would shortly present said speech in front of an audience while being filmed.

The heart rates of men in the placebo group jumped but those of men treated with cortisone remained steadier. And although the heart rates of members of both groups rose during the test itself, the men who had received cortisone returned to their normal heart rate more quickly after an ordeal that also included a surprise arithmetic task in front of the same audience. The researchers also noted that subjects in the placebo group who had higher natural levels of the glucocorticoid reported experiencing less fear than their peers did.

De Quervain and his colleagues then tested this effect in men and women afraid of spiders, administering 10 milligrams of cortisone one hour before showing them a picture of a furry spider with a legspan of more than five inches. Over the course of two weeks the 20 subjects saw the picture six times, and the 10 who had been dosed with stress hormones reported 45 percent less fear than their peers did, even when deprived of cortisone treatment before the last session. Furthermore, taking the stress hormone did not seem to impact any other aspects of their personality, such as mood; it simply diminished the experience of the phobia.

"Repeated administration of glucocorticoids induced a progressive reduction of fear ratings and, thus, might have facilitated the extinction of phobic fear," the team wrote in this week's issue of Proceedings of the National Academies of Science. "Our findings indicating that elevated glucocorticoid levels in the context of a fearful situation turn down fear symptoms in phobic subjects suggests that cortisol release may represent an adaptive response."