July 7 (HealthDay News) -- A common health-food supplement might help ease the urges of people with a compulsive hair-pulling disorder called trichotillomania, U.S. researchers report.

They tested the effectiveness of the amino acid N-acetylcysteine in a 12-week study that included 50 people with an average age of 34. Most had started compulsive hair pulling by age 12.

Some participants were given 1,200 milligrams of N-acetylcysteine every day for the first six weeks and 2,400 milligrams a day for the next six weeks. Others were given a placebo.

After nine weeks, hair pulling was significantly reduced among those taking the supplement. After 12 weeks, 56 percent of the participants taking the supplement reported feeling much or very much improved, compared with 16 percent of those taking the placebo.

The results appear in the July issue of Archives of General Psychiatry.

"Trichotillomania is compulsive in the sense that people can't control it," principal investigator Dr. Jon Grant, an associate professor of psychiatry at the University of Minnesota, said in a news release from the journal. "People feel unable to stop the behavior, even though they know it is causing negative consequences. Some people don't even know they are doing it."

"There are people who have tried all kinds of things that have never worked," Grant said. "The reality is that if you pull your hair and it is on a noticeable part of the body, people are really disabled by this. It's not easy to go out in public if people are noticing your bald spots. Self-esteem is a huge problem. This supplement may offer hope."

N-acetylcysteine lowers brain levels of glutamate, a chemical that triggers excitement.

SOURCE: JAMA/Archives journals, news release, July 6, 2009