Many people think of nail biting as a nervous habit, but the driving force may not be anxiety. Mounting evidence shows that people who compulsively bite their nails, pick their skin or pull their hair are often perfectionists, and their actions may help soothe boredom, irritation and dissatisfaction.

As many as one in 20 people suffer from body-focused repetitive disorders, engaging in behaviors such as biting their nails or plucking out hair until they damage their appearance or cause themselves pain. These disorders are related to tic disorders and, more distantly, obsessive-compulsive disorder. As such, the repetitive behavior is extremely difficult to quit—yet many people continue to think they simply have a nervous habit and are too weak-willed to overcome it.

A new study adds evidence to a theory that perfectionism rather than anxiety is at the root of these behaviors. The researchers first surveyed 48 participants, half of whom had these disorders and half of whom did not, on their organizational behavior and ability to regulate their emotions. Those with the disorders scored as organizational perfectionists, indicating a tendency to overplan, overwork themselves and get frustrated quickly without high levels of activity.

Researchers then put the subjects in situations designed to provoke four different emotions: to incite stress, they showed a movie of a plane crash; to promote relaxation, they showed a movie of waves; to elicit frustration, they presented a difficult puzzle but said it was easy; and to evoke boredom, they made participants sit in a room alone. People who had the disorders engaged in the body-focused behaviors during all the situations except the relaxing movie.

The work, which was published earlier this year in the Journal of Behavior Therapy and Experimental Psychiatry, jibes with a recent theory that stress is far from the sole cause of these compulsions. Boredom and frustration, easily elicited by an underlying perfectionist personality, may be more important triggers. Past research suggests that the biting or scratching indeed makes people feel better temporarily—perhaps satisfying the perfectionist urge to be doing something rather than nothing. After the initial relief, however, comes pain, shame and embarrassment.

The findings could help therapists treat patients who suffer from the disorders; studies have shown that these types of perfectionist beliefs and behaviors can be eased with cognitive-behavior therapy. If patients can learn to think and act differently when tension builds, they may be able to stop the urge before it starts.