Faulty gene linked to hair pulling disorder

Sep 27 2006

An unusual and uncommon psychiatric disorder that compels people to pull out their hair is now thought to be caused by a mutant gene.

Scientists at Duke University Medical Center say they have identified gene mutations that causes the disorder trichotillomania which affects between 3 percent and 5 percent of the population.

Trichotillomania is considered an impulse control disorder and sufferers have noticeable hair loss or patches of baldness, but they often disguise their habit and the disorder often goes undiagnosed and untreated.

The disorder is often accompanied by other psychiatric conditions, such as anxiety, depression, obsessive compulsive disorder or Tourette syndrome, which are better known than the hair-pulling behavior.

The research team found two mutations in a gene called SLITKR1 that were implicated in trichotillomania patients but say the mutations account for only a small percentage of trichotillomania cases.

Nevertheless the findings are significant because they expose a biological basis for mental illnesses which are as a rule blamed on a person’s upbringing or life experiences.

Lead study investigator Stephan Züchner, M.D., assistant professor of psychiatry and researcher at the Duke Center for Human Genetics says psychiatric conditions carry negative perceptions in society.

Züchner believes if science can demonstrate such disorders have a genetic origin, diagnosis can be improved and new therapies developed which will in turn reduce the stereotypes associated with mental illness.

At present there is no specific treatment for trichotillomania, although it is sometimes successfully managed with drugs used for depression and anxiety disorders.

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.

When they looked further the team found two mutations in the SLITRK1 gene among some individuals with trichotillomania but not in their unaffected family members.

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

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

Ashley-Koch says such discoveries could open the door for genetic testing, which is completely unheard of in the field of psychiatry.

According to the National Institutes of Mental Health, psychiatric illnesses affect one in four Americans and are the leading cause of disability for Americans between the ages of 15 and 44.

The most common disorders are depression and anxiety disorders, such as panic disorder, obsessive compulsive disorder and social phobia.

The research was self-funded through Duke University; October 1-8, 2006, is National Trichotrillomania Awareness Week.

The findings will be published in the October issue of Molecular Psychiatry.