The Psychology of Nail Biting

Nail chewing and biting belongs to a group of compulsive skin picking and nail biting behaviors (also known as onychophagia).  While not typically serious,  any obscessive or compulsive behavior can have damaging effects on self esteem. It typically occurs in:

  • 28% to 33% of children 7-10 years
  • 44% of adolescents
  • 19% to 29% of young adults
  • 5% of older adults
  • Is most common in young males

Compulsive nail-biters continually bite their nails past the nail bed and bite or pick at cuticles until they bleed and constantly have red, sore, and sometimes infected fingers. Nail-biters keep their hands hidden, apply Band-Aids, and prefer winter because they can wear gloves.. It's quite normal to feel shame and social embarrassment feeling your nail chewing has gotten out of hand.  Especially when your fingers are raw and bleeding.  Often a nail biter will be frustrated at why they can't stop and they will wonder whether or not they are crazy.

There is a similarity between nail chewing and trichotillomania (repetitive hair pulling).  Some do it in an automatic way, as if they are spaced out and not really thinking about what they are doing. And sometimes they do it when they are involved in some other activity at the same time such as reading, talking on the phone, working at the computer, watching TV, etc. Then with others, the deliberate picking or biting is their main activity at the time, and they will frequently interrupt other activities more than normal to clip hangnails, bite a rough edge or just fidget.

There is also a strong correlation between the various purposes behind nail biting and hair pulling. At a basic level level, they satisfy an urge. Many report an almost compulsion or need to do them. Pulling, picking or biting also often deliver a relaxed and pleasurable feeling when stressed. Doing these things has a kind of soothing effect on their nervous systems, and reduces levels of stimulation. On the other hand, when they are bored or inactive, they seems to provide a needed level of stimulation to the nervous system. So in some way, this behavior is a way of self-regulating the nervous system.  This is why many people, though they hate the fact that they bite their nails, can't quit. It "feels good" at the time, regardless of  the consequences or how painful their nailbeds become. It may reall be about self-regulation of a nervous system that may not be self-regulating very well.

With some people, it may also involve a kind of compulsive perfectionism. Nail-biters will often try to bite off rough-feeling or broken bits of cuticle or nail sticking out in order to make their nails feel smooth and look "perfect".  A small imperfect edge is "permission" to chew at or pull on the offending piece of nail.  Paradoxically, in trying to make the nail look perfect, it ends up looking much worse.

A theory is that some out-of-control grooming mechanism in the brain underlies the need to chew nails. Another theory is that this behavior represent an attempt to control these internal stimulation levels externally. Most nail biters have difficulty refraining from chewing when thery are either overstimulated (dus to stress or excitement) or understimulated (due to boredom or inactivity). Similar behaviors can be observed in animals who are kept in confined or unstimulating environments, or who live in stressful conditions.

One theory is that compulsive hair pulling, skin picking, and nail biting form a subgroup of what is becoming known as the Obsessive- Compulsive Disorder. Previously OCD was thought to be only a single disorder. It may instead represent a range of related disorders:

  • Body Dysmorphic Disorder
  • Anorexia Nervosa, Bulimia
  • Compulsive Nail Biting
  • Trichotillomania, Onychophagia,
  • Compulsive Skin Picking
  • Tourette's Syndrome.

Recently, a new term has been coined for these problems - Body-focused Repetitive Behaviors (BFRBs). Therefore, nail-biting is considered to originate within the chemistry of the brain and may be caused by the person's genetics.  Another theory is that a vitamin deficiency is to blame and nail biting has been successifully treated with the B-vitamin inositol which seems to reduce the urge to pull or pick.  

Habit Reversal Training is another method to attempt to reverse this behavior.  It is important to accept that they will not simply be overcome in a few days or weeks as this behavior has been going on for a long time. Also, you are fighting the fact that they feel good to do providing some short range satisfaction and soothing stimulation.  Nail biting can be overcome if you have the motivation. More important is learning to improve your self esteem. Sometimes just knowing "why" is helpful.  You aren't crazy, it's HARD to stop.   Nail biting is a chronic problem, so there currently isn't a 'cure', but if you are determined and keep trying, you can learn to change your behavior.


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