Most everyone plays mindlessly with their hair from time to time. But for some people it becomes such an uncontrollable compulsion that they end up with bald patches or eyebrows plucked bare.

If it's any comfort, animals too suffer from "grooming compulsions."

Though the behavior is documented in the Bible and ancient medical texts, treatment for hair-pulling has not been studied much. But now a University of Minnesota researcher might have found an answer in a common, over-the-counter nutritional supplement that costs about $15 for 100 pills.

Better yet, his breakthrough could hold promise for a whole range of common obsessive behaviors, from nail-biting to hand-washing.

Dr. Jon Grant, a psychiatrist who specializes in addictive and compulsive behaviors, found that an antioxidant called N-acetylcysteine (NAC) helped about half of the hair-pullers in his study. Some engaged the behavior less often, and some quit altogether.

It's not a cure-all, Grant said, because it didn't work in the other half of his subjects. Still, the study, published Monday in the Archives of General Psychiatry, is important because it shows for the first time that reducing a certain chemical in the brain also eases an uncontrollable behavioral obsession.

Extreme hair-pulling is relatively uncommon compared to other grooming compulsions such as nail-biting, he said, but it occurs in all cultures and in animals.

"Dogs lick themselves to the point of hair loss," he said. "Parrots pull out all their feathers."

Some studies have shown that anywhere from 1 to 4 percent of people engage in hair-pulling at some point in their lives, more often in women than men. Like most obsessive behaviors, it's probably genetic. But the people who suffer from it often suffer in silence and shame, Grant said.

The most extreme cases, he said, "have difficulty hiding the bald spots," he said. "They wear false eyelashes or pencil in their eyebrows. Over time it's led them to not date, or get married, or socialize."

One of the women in his study picked at her hair for six or seven hours a day. She asked to be identified only by her first name, Jacqueline, because she didn't want others to know her problem. She picked her hair during meetings at work, and then after dinner she'd sit for hours picking split ends. She didn't get bald, but her hair became noticeably thinner.

"I felt guilty because I couldn't stop," she said. "I wasn't living my life."

The only current treatments for obsessive behaviors are antidepressants, which don't work well, and counseling, which doesn't always work.

For some time researchers have hypothesized that the brain chemical glutamate might be a cause because it's linked to excitation, reward and motivation. It's part of the vicious brain-chemistry cycle in addiction. Grant decided to try NAC, an amino acid that does not come in any kind of food, because it's known to suppress glutamate. He decided to focus on hair pickers because "it was a greatly under-served population of people."

He found 50 obsessive hair pickers. Half got a sham drug, half got NAC -- 2,400 milligrams a day. After three months, 56 percent of those on the drug showed noticeable improvement compared to 16 percent on the placebo.

After taking the drug for three weeks, Jacqueline stopped hair picking almost altogether. She recognized she was getting the real therapy, not the placebo. "There is no way that my mind is powerful enough to stop something like that," she said. "I couldn't believe it."

There is now a much larger study of NAC headed by researchers at Yale University to see if it works on a broader range of obsessive behaviors.

Grant said he believes some might be helped and others won't because of differences in how people metabolize the chemical.

But one obsessive nail -biter in his office who was initially a skeptic is now a convert.

"He was my biggest critic, but after two-and-a-half months he actually had nails again," Grant said.

Josephine Marcotty • 612-673-7394