According to a new study published in the Archives of General Psychiatry, an amino acid available in health-food stores reduced repetitive hair pulling in patients with trichotillomania, a compulsive disorder characterized by the recurrent pulling out of one's hair that results in noticeable hair loss.

The over-the-counter supplement called N-acetylcysteine, showed significant reductions in hair pulling symptoms with over half the people participating in the study finding relief from their compulsion.

The study was conducted by researcher Jon Grant and colleagues at the Minnesota School of Medicine in Minneapolis who tested N-acetylcysteine, an amino acid available in health food stores and also sold by prescription for other purposes on 50 people with trichotillomania.

"This study, the first to our knowledge that examines the efficacy of a glutamatergic agent in the treatment of trichotillomania, found that N-acetylcysteine demonstrated statistically significant reductions in trichotillomania symptoms," wrote Grant and colleagues.

The 12 week double-blind controlled trial involved 45 women and five men between ages 18 to 65 with trichotillomania. Twenty-five participants were randomly assigned to a daily dose of 1,200 milligrams of N-acetylcysteine which was doubled after six weeks if no improvement occurred. The remaining 25 were given a placebo. Hair-pulling symptoms were measured by the Massachusetts General Hospital Hair Pulling Scale and the Psychiatric Institute Trichotillomania Scale (P=0.001).

"Fifty-six percent of patients were 'much or very much improved' with N-acetylcysteine use compared with 16 percent taking placebo," the researchers wrote in their report.

Researchers noted significant improvement in hair pulling among those who took the amino acid after nine weeks, and no adverse events were reported.

"By design, this study did not assess treatment effects beyond the 12-week treatment period, and the longer-term effects of N-acetylcysteine therapy require further evaluation," the authors wrote. "It is possible that a longer course of therapy could result in continued and even greater reductions in trichotillomania symptoms."

The researchers said there are types of hair-pulling that may respond better to other drugs and to talk therapy, referring to the 44 % of people who did not respond to the treatment.

They added that the amino acid shows promise as a convenient and affordable treatment for trichotillomania, since it is available in health-food stores, costs less than most insurance copayments and did not show adverse reactions.

They noted that "this study did not include behavioral therapy. Cognitive behavior therapy has shown benefit for trichotillomania and should be considered in conjunction with pharmacotherapies."

"As effective treatments for hair pulling emerge," they wrote, "it becomes increasingly important that physicians and mental-health care providers screen for trichotillomania to provide timely treatment."

The researchers called for further study into the effectiveness of N-acetylcysteine at higher dosages and its use in the long-term treatment of trichotillomania.