The last thing you'd expect to see a person with a severe fear of spiders doing is holding an enormous, creepy tarantula in the palm of her hands. But that's exactly what happened to one woman and ten other clinically-diagnosed arachnophobics who participated in an exposure therapy study at Northwestern University.

The study was conducted at the University's Feinberg School of Medicine by neurology postdoctoral fellow Katherina Hauner, and featured 12 adults diagnosed with arachnophobia, (the anxiety disorder categorized as a specific fear of spiders), recruited to evaluate the immediate and long-term impact of brief exposure therapy on the brain.

How the Study was Conducted

Published in the Proceedings of the National Academy of Sciences, the research entailed administering a single two-hour exposure therapy session to each participant, gradually exposing them to a caged tarantula named Florence. During the session, the scientists explained that tarantulas are neither evil nor intent on hurting others; in fact, they are delicate creatures that tend to fear people and want to hide.

At first, many participants stayed far from the tarantula, experiencing typical anxiety symptoms such as agitation, sweating and pounding heartbeat. As the session progressed, however, nearly all of them approached, touched and eventually held the spider.

Even more promising to researchers was the fact that when reunited with the giant arthropod six months later, the same participants still exhibited no fear, approaching and petting the spider with ease.

Hauner explained that fear is often rooted in a perceived lack of control; the participants may have been able to overcome their anxiety by learning they could anticipate the spider's predictable behaviors, and thus establish a sense of control.

The Science Behind the Changes

In order to monitor brain changes, MRI scans taken at the onset of the study (when the participants struggled to even look at pictures of spiders) showed excessive responses in the regions responsible for fear response. But when they revisited the pictures immediately after the therapy, the brain scans showed a marked decrease in activity.

However, those regions did not sustain those changes six months later, even though the fear response was no longer evident. The results led Hauner to suggest there may be different brain mechanisms associated with short-term versus long-term fear reduction.

Phobias and Exposure Therapy

A specific phobia is a type of anxiety disorder characterized by a fear of a particular object or event, severe enough that it interferes with daily function. Those with phobias of spiders, for example, might go to great lengths to avoid walking on grass, or avoid going home for days if they thought a spider might be lurking.

Examples of other specific phobias include: fear of darkness, heights, enclosed spaces, needles, thunder and lighting and fear of developing an illness. The National Institute of Mental Health reports that about 8.7 percent of adults struggle with at least one specific phobia, though it is not clearly understood what causes them to develop.

Exposure therapy aims to desensitize patients by gradually exposing them to the object of their fears. It is frequently employed in the treatment of various phobias, as well as to address social anxiety disorder and Obsessive-compulsive Disorder. It is designed to train the brain to stop sending fear signals, which is highly likely to have happened in this particular study.

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