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Way up high. A scene from a virtual reality environment used to treat people who are afraid of heights.

Images courtesy of DCN, University of Basel

Damping Down Fear With Cortisol

Fear of heights can drive people to extremes, from crossing the country by bus to avoid flying to commuting extra hours every week to circumvent a high bridge. A new study now suggests one counterintuitive path to relief: The human stress hormone cortisol seems to improve the effectiveness of behavioral therapy to help people overcome their fear of heights.

The standard treatment for many phobias involves exposing someone to the source of their fear in a safe environment—either in real life or, increasingly, using virtual reality. When nothing bad happens, that person gradually learns that the source—whether it's heights, snakes, or enclosed spaces—is safe. In a process called "extinction," new memories of safe experiences prevail over ingrained memories of scary ones.

The treatment works, but it can take many repetitions to stick and is unpleasant enough that some patients drop out. So researchers have been looking for drugs that might be used in combination with extinction-based therapy and can help speed it up. One drug called D-cycloserine, which helps new memories form, is being tested in clinical trials in people with certain phobias. But human and animal studies have shown that hormones released during stressful situations go one step further, not only promoting the creation of new "safe" memories but also inhibiting fear memories, says cognitive neuroscientist Dominique de Quervain of the University of Basel in Switzerland, who lead the present study, published today in the Proceedings of the National Academy of Sciences.

This may seem counterintuitive, because stress hormones are released during difficult moments, but they have a variety of other roles as well. Those include helping consolidate memories of new information and making it more difficult to retrieve existing memories.

De Quervain's team treated 40 people with acrophobia, or a fear of heights, with three sessions of exposure therapy, giving half of them cortisol pills before treatment and the other half a placebo. The patients were exposed to heights in a virtual environment in which they had to ascend tall elevators, walk over bridges, and the like. "It's a pretty scary thing, actually, if you are afraid of heights. I've done it myself. I only have a little fear of heights, ... and it works," de Quervain says.

In a questionnaire given before and a month after treatment, the participants who received cortisol rated their fear an average of 24 on a scale of 1 to 120, down from 58; those who got a placebo said their fear dropped to 35, on average, from a starting point of 59. This translated to about a 60% drop in those who got cortisol and a 40% drop in those who didn't. And when they ascended a virtual elevator a month after treatment, the participants who had received cortisol showed just one-fifth the increase in skin conductance—an indicator of arousal—compared with subjects who had received the placebo.

More specific phobias, such as fear of heights or spiders, are easier to treat in a therapeutic setting than generalized ones, such as social phobia, obsessive-compulsive disorder, or posttraumatic stress disorder, de Quervain says. Theoretically, cortisol should be useful in treating both specific and general varieties, but more research is needed to test it, he says.

"It's a really new way to combine medication with psychotherapy" as a way to erase debilitating phobias, says Michael Davis, a neuroscientist at Emory University in Atlanta who studies D-cycloserine. He says cortisol looks promising and suspects it may eventually follow D-cycloserine down the road to clinical trials.

Praising the new study as an impressive validation of cortisol and a solid first step toward eventual clinical use, Roger Pitman, a research psychiatrist who studies posttraumatic stress disorder at Harvard Medical School and Massachusetts General Hospital, both of which are in Boston, says one lingering question is how well cortisol compares with D-cycloserine. "Now it remains to be seen whether cortisol does as well, or not as well, or possibly better. Or maybe combining the two of them might even give stronger results," Pitman says.