The researchers found that participants engaged in repetitive behaviors when under stress or when they felt bored or frustrated, but not when they were relaxed.
"Chronic hair-pulling, skin-picking disorder and nail-biting and various other habits are known as body-focused repetitive behaviors. Although these behaviors can induce important distress, they also seem to satisfy an urge and deliver some form of reward,'' says principal investigator Kieron O'Connor.
O'Connor and colleagues studied 24 individuals with these repetitive behaviors and compared them with 24 control subjects who did not have body-focused repetitive behaviors.
The participants completed questionnaires to assess emotions such as boredom, anger, guilt, irritability and anxiety, and also took part in a clinical evaluation conducted over the phone.
Next, the participants were exposed to different experimental situations, each designed to stir one of four emotions:
In some cases, these experimental situations involved the participants viewing videos - such as of a plane crash (stress) or waves on a beach (relaxation). To prompt frustration in the participants, the researchers set their subjects a task that was described as "easy and quick," but which in reality was difficult and long. To provoke boredom, they simply left the participant in a room on their own for 6 minutes.
The team found that, during the boredom and frustration experiments, subjects with a history of body-focused repetitive behaviors reported a stronger desire to engage in the behaviors. However, participants were not more likely to pull their hair, bite their nails or pick their skin during the relaxation experiment.
According to the authors of the study - which is published in the Journal of Behavior Therapy and Experimental Psychiatry - these results confirm that participants engage in these behaviors when under stress or when they feel bored or frustrated, and as such are not simply "nervous" habits.
Repetitive behaviors may be 'perfectionistic'
O'Connor explains the study's findings:
"We believe that individuals with these repetitive behaviors may be perfectionistic, meaning that they are unable to relax and to perform tasks at a 'normal' pace. They are therefore prone to frustration, impatience and dissatisfaction when they do not reach their goals. They also experience greater levels of boredom."
"The findings suggest that individuals suffering from body-focused repetitive behaviors could benefit from treatments designed to reduce frustration and boredom and to modify perfectionist beliefs," concludes first author Sarah Roberts.
A 2006 study by scientists at Duke University Medical Center in Durham, NC, suggested that gene mutations may cause compulsive pulling of the hair, also known as trichotillomania.
Trichotillomania affects 3-5% of the general population and often results in noticeable patches of baldness, though people with this impulse control disorder - which may be accompanied by anxiety, depression, obsessive compulsive disorder or Tourette syndrome - often do not seek treatment.
The Duke researchers identified an association between two mutations in the gene SLITKR1 and trichotillomania, although the scientists said the mutations only account for a small percentage of trichotillomania cases.
However, as impulse control disorders are typically blamed on a person's upbringing or life experiences, these findings were considered significant as they offered a biological basis for these conditions.