MONDAY, March 28 (HealthDay News) -- Adding the stress hormone cortisol to more traditional exposure therapy may help anxious patients overcome their fear of heights, researchers say.

Exposure therapy involves gradually exposing people to the thing they fear -- be it height or spiders -- in order to reduce fear responses.

But while promising, this experimental treatment is not yet ready for prime time, said the authors of a study published online March 28 in the Proceedings of the National Academy of Sciences.

"This is a first study -- a proof of concept, if you wish," said study lead author Dr. Dominique J.-F. de Quervain, director of cognitive neuroscience at the University of Basel in Switzerland.

"We now need more studies to explore the therapeutic potential of cortisol in combination with psychotherapy in the treatment of anxiety disorders," de Quervain said.

The study involved 40 people with clinically diagnosed acrophobia -- fear of heights -- all of whom took three "virtual" outdoor elevator rides.

An hour before experiencing each fear-inducing situation, half of the participants took 20 milligrams of cortisol, while the other half took an inactive placebo.

Their reactions were assessed three to five days and one month after the last elevator ride, or exposure session.

Those who took cortisol suffered less anxiety than those who took the dummy drug. This was evident in their answers to a standard acrophobia questionnaire and through skin conductance tests, which measure how well the skin conducts electricity. The skin is thought to be a better conductor when the body is aroused and producing sweat.

The authors also reported that cortisol could reduce social and spider phobias.

But why would adding a stress hormone actually reduce fear? Aren't these the hormones produced when people are in anxiety-provoking situations?

The answer to the latter question is yes, but cortisol plays a more complicated role in learning and memory, which might explain this benefit.

They are able to recall the incident, but their body remembers the way it felt to be fearful and those physical feelings are re-experienced when thinking about the incident, explained Keith Young, vice chair for research of psychiatry and behavioral science at Texas A&M Health Science Center College of Medicine and core leader for neuroimaging and genetics at the Center of Excellence for Research on Returning War Veterans in Temple.

Rather, they're remembering subsequent episodes of fear, Young said.

And it's those memories that need to be overwritten and replaced with new, better ones. "Enough of the old memory is there to remember the incident, but not enough to remember and trigger the fearful feelings," Young said.

"Cortisol inhibits retrieval of the fear memory and promotes the storage of corrective experiences," said de Quervain.

Other researchers have had enough success that Young's group is starting to do clinical research on the idea.

More information

The U.S. National Institute on Mental Health has more on anxiety disorders.