Originally posted at Field of Science on April 21, 2011, where it was a Research Blogging Editor's Selection.

Earlier this week I shared the story of my specific phobia of vomiting, and today I'm going to blog about an article recently published in PNAS (open access!) about the efficacy of cortisol supplementation during exposure therapy for specific phobias.

Cortisol, which I have blogged about before, is a major endocrine involved in the human stress response (corticosterone, a closely-related steroid, serves the same purpose in many other animals). Stressful experiences are also learning experiences for many individuals ("I'll never do that again..." etc.), and cortisol seems to have an impact on the building and retrieval of memories. Specifically, it appears to promote the storage of new memories while simultaneously repressing the retrieval of already stored memories. This makes it a potentially beneficial supplement during exposure therapy, which is based on replacing traumatic memories of objects, events, or situations with repeated non-traumatic exposures to "unlearn" the fear.

In this study, the authors compared two groups of people undergoing exposure therapy for their fear of heights: a control group that received a placebo and an experimental group that received 20mg of cortisol one hour before their treatment sessions. (The two groups did not differ in baseline levels of cortisol, and the experimental group did have higher levels of circulating cortisol, both validated by saliva samples.)

Exposure therapy reduced self-reported fear in both groups, but the effect was amplified in the cortisol group, both 3-5 days after treatment and at follow-up a month later. This suggests that cortisol supplementation increases the efficacy of exposure therapy in people who have specific phobias of heights. However, more studies need to be done to see if the cortisol treatment has continuing long-term effects in the fear response.

I hesitate to jump for joy because I have no idea if exposure therapy (with or without cortisol) would be effective or even possible for my specific phobia. I am not sure how well these results can be extrapolated to other specific phobias, although previous research suggests it may also be beneficial in arachnophobia and social phobia.

de Quervain, D., Bentz, D., Michael, T., Bolt, O., Wiederhold, B., Margraf, J., & Wilhelm, F. (2011). Glucocorticoids enhance extinction-based psychotherapy Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.1018214108