WASHINGTON (Reuters) - People with a disorder in which they are convinced they are ugly have a brain glitch when processing things they see, researchers said on Monday.

The findings, published in the journal Archives of General Psychiatry, shed light on body dysmorphic disorder, marked by a dramatically distorted self-image and obsessive thoughts about imagined or minor defects in their appearance.

An estimated 1 to 2 percent of people around the world have this condition, also called BDD, according to Dr. Jamie Feusner, a professor of psychiatry at the University of California at Los Angeles who led the research.

Some undergo repeated cosmetic surgery procedures in a futile attempts to fix the problems.

The cause of the disorder remains unknown, with experts suspecting that a variety of factors may contribute, from genetics to upbringing.

People with BDD often think of themselves as ugly or disfigured and may obsess about physical traits or minor and imagined flaws even when assured by others they look fine. About a quarter of people with BDD attempt suicide.

Feusner’s team performed functional magnetic resonance imaging, or fMRI, brain scans on 12 people with the disorder as they viewed black-and-white images of other people’s faces, and compared the results to those of people who do not have BDD.

They saw differences in how the right and left sides of the brain worked in people with BDD, but no actual structural differences in the brain.

“This is the first time where there’s evidence that there is kind of a biological abnormality that may be contributing to the symptoms -- the distorted body image -- in body dysmorphic disorder,” Feusner said in a telephone interview.

All were shown three pictures: a black-and-white photo of a face with a neutral expression, a black-and-white blurry image of a face, and a black-and-white image looking like a detailed line drawing of a face.

The brain scans showed that the people with BDD relied much more heavily on their brain’s left side than the right side.

“The left side of the brain really is really specialized for doing more detailed and analytic process, whereas the right side of the brain processes more holistically and globally,” Feusner said.

People with BDD tend to fixate on their face and head, although other body parts can be involved. The disorder tends to run in families and appears in both men and women. It is more common in people with obsessive-compulsive disorder.

“It affects them so they often can’t leave their house or function very well at work; they can’t have relationships because of this concern: usually they’re thinking about their appearance in some way multiple hours a day, checking the mirror, looking into cosmetic procedures,” Feusner said.

Feusner said one patient he knew had undergone five nose jobs. Others get repeated breast augmentations or chin and cheek implants. Feusner said one woman got so many procedures that “she doesn’t even look like a human being anymore.”

And invariably they are dissatisfied with the surgery and can end up feeling even more hopeless afterward, he said.