Help may be at hand for those who run screeching from the room at the sight of a spider, or who have cold sweats at the thought of speaking in public.
Researchers at Zurich University have discovered that the stress hormone cortisol can help reduce fear of spiders and social phobia.
All phobias are characterised by a marked and disproportionate fear of certain objects and situations.
Dominique de Quervain, leader of the study, chose spider and social phobias because they are very common.
Cortisol is produced in situations of stress, but is not always present in sufferers of phobias, he said.
"Cortisol is a stress hormone, triggered by stress and phobic stimuli but it usually takes ten to 15 minutes before this hormone is in the bloodstream," de Quervain told swissinfo.
"The stimulus is often gone by that time because a person who is spider phobic, for example, has left the situation. This means the hormone cannot really act at the moment of exposure," he explained.
De Quervain and his team administered the hormone to two sets of volunteers in tablet form one hour before exposure to the phobic stimulus. In this way, cortisol levels were elevated at the time the stimulus was introduced.
"Cortisol is designed to help humans in stressful situations and if a situation is getting chronic, such as in prolonged exposure to a phobic stimulus, then this hormone works to lower fear," he said.
A group of 40 people with social phobias was therefore given a cortisol tablet one hour before they had to make an unprepared speech.
Those who received the hormone reported significantly reduced levels of fear about the speech, compared with those who received a dummy version.
Researchers also gave 20 people with arachnophobia a dose of cortisol before their nerves was tested. They found that the hormone successfully reduced anxiety when the group was shown pictures of spiders.
The participants saw a progressive reduction in fear during each session over the two-week period of the study. In fact, the fear-reducing effect was still in evidence two days after the last dose of cortisol.
De Quervain, who has spent years investigating the effects of cortisol on memory and related behaviours, is already looking ahead to his next research project.
"We are planning to do a study in combination with behavioural therapy to see whether pre-elevated cortisol levels help facilitate the effectiveness of the therapy."
The findings of the Zurich University research project appear this week in the science journal – Proceedings of the National Academy of Sciences.
Cortisol is a stress hormone produced by the body in response to stressful situations.
The subjects who took part in the research answered a newspaper advertisement.
The study was supported by the Swiss National Science Foundation.
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