Hair-Pulling Disorder Caused by Faulty Gene in Some Families

Scientists at Duke University Medical Center have identified gene mutations that cause trichotillomania, a psychiatric disorder that triggers people to compulsively pull their hair.

The Duke team found two mutations in a gene called SLITKR1 that were implicated in trichotillomania patients.

The mutations account for only a small percentage of trichotillomania cases, said the scientists.

However, their findings are significant because they validate a biological basis for mental illnesses.

Such illnesses have long been blamed on a person's upbringing or life experiences, said lead study investigator Stephan Z|chner, M.D., assistant professor of psychiatry and researcher at the Duke Center for Human Genetics.

"Society still holds negative perceptions about psychiatric conditions such as trichotillomania," Z|chner said.

"But, if we can show they have a genetic origin, we can improve diagnosis, develop new therapies and reduce the stereotypes associated with mental illness."

Results of this study will appear in the October 2006 issue of the journal Molecular Psychiatry.

The Duke scientists studied 44 families with one or more members who had trichotillomania.

The researchers studied SLITRK1 because it was linked last year to a related impulse-control disorder called Tourette syndrome, which causes repetitive behaviors such as blinking, throat-clearing or shouting obscenities.

The parent of one Tourette patient carried the SLITRK1 mutation but displayed only symptoms of trichotillomania, not Tourette.

The Duke team further studied SLITRK1 and found two mutations in the SLITRK1 gene among some individuals with trichotillomania but not in their unaffected family members.

Mutations are changes in the structure of a gene that alter how the gene behaves. The researchers estimate that the SLITRK1 mutations account for 5 percent of trichotillomania cases.

The SLITRK1 gene is involved in forming connections among neurons, or brain cells.

The researchers hypothesize that the two mutations in SLITRK1 cause neurons to develop faulty connections and that this faulty "wiring" produces the urge to pull one's hair.

While SLITRK1 is the first gene linked with trichotillomania, numerous other genes likely contribute to this disorder and other psychiatric conditions, said senior study investigator Allison Ashley-Koch, Ph.D., assistant professor of medical genetics and researcher at the Duke Center for Human Genetics.

"The SLITRK1 gene could be among many other genes that are likely interact with each other and environmental factors to trigger trichotillomania and other psychiatric conditions," Ashley-Koch said.

"Such discoveries could open the door for genetic testing, which is completely unheard of in the field of psychiatry."

Compared with neurological diseases, the identification of genes which underlie psychiatric disorders have only just begun, she said.