When reality T.V. gets people to eat bugs, the reaction is usually more disgust than fear. Researchers suspect a heightened sense of disgust also plays a role in compulsive behavior.

Gilda Leiter, 52, has obsessive compulsive disorder or OCD. She's constantly washing and cleaning to avoid germs. She gags easily and if her partner gets sick, “If he throws up, I throw up, that’s my reaction, because vomit makes me vomit."

OCD is considered an anxiety disorder but new research challenges the traditional view that fear is the driving force.

"OCD is often, seems to be driven by other emotions like disgust, that disgust sensitivity around avoiding things, particularly with contamination issues,” said Narthan Shapira, M.D., Ph.D. “OCD might be more relevant to the illness." (:14)

A University of Florida study compared brain images of healthy volunteers and OCD patients as they viewed neutral, fear-inducing and disgusting images. The two groups had different brain responses.

"The OCD subjects when they see fear, it looks very similar to the healthy volunteers but when they see disgust the pattern is much more intense,” Dr. Shapira said.

Now Gilda manages her OCD with medication. "It's helped me tremendously. It’s relieved a lot of the panic and the anxiety and I function much more normally."

But drugs don’t work for everyone.

"About half the people will get mild to moderate response to typical treatments and a little less than half will get essentially no response,” Dr. Shapira continued. “We have an illness where there's a lot of work needs to be done."

Fear and disgust affect different parts of the brain. Understanding the “disgust factor” may help doctors see OCD in a new way.

Researchers say it's too early to say whether these studies will lead to better ways to treat OCD.