The American Psychiatric Association plans to include nail-biting as a form of obsessive-compulsive disorder - also known as OCD - in its Diagnostic and Statistical Manual revision for 2013. The disorder, known as onychophagia, will join hair-pulling, skin-picking and other pathological grooming habits in the OCD classification.
"I've seen people who have bloody stumps," said Keri Maki, a master nail technician in Minnetonka, Minnesota. "The nail bed is bitten back to almost nothing, there are scabs around the cuticle. It's pretty disgusting."
Nail-biting is currently listed in the manual's "not otherwise classified" section of disorders.
The association isn't saying that all nail-biters are obsessive-compulsive. In fact, up to 48 per cent of adults do it, but some have moved beyond nail-biting as a habit and into what is called clinical severity - the point at which the action is so severe that there is physical damage.
Experts say people bite their nails for a variety of reasons: out of boredom, as a way to soothe themselves when they feel anxious, stressed, or even as a symptom of perfectionism - using the teeth to reshape an uneven nail.
Treatment includes the use of bitter-tasting polish, keeping nails manicured or in more severe cases, medication and counselling.
