An Oral Parafunctional Habit
Nail biting (onychophagia) is an oral parafunctional habit—the use of the mouth for a purpose other than speaking, eating, or drinking, a category that includes bruxism (grinding teeth), digit sucking, pencil chewing, and mouth breathing. Nail biting begins during childhood, increases substantially during adolescence, and declines with age, although the habit may continue into adulthood.[1,2,3,4,5,6,7,8,9] The considerable increase in onychophagia in teens may be explained by the difficulty of transitional phases in an individual's life, and the feeling of instability associated with those phases.
According to the Diagnostic and Statistical Manual of Mental Disorders, fifth edition, nail biting is classified with "obsessive-compulsive and related disorders."[10,11] In the 10th edition of the International Classification of Diseases, nail biting is classified with "other specified behavioral and emotional disorders with onset usually occurring in childhood and adolescence," such as thumb sucking, excessive masturbation, and nose picking.
The Causes of Nail Biting
Nail biting is an underrecognized habit, and its precise cause is debatable.[7,10,12,13] The causes of onychophagia may include psychological, acquired, or familial factors, although it is unknown whether familial factors relate to imitating the nail-biting behavior of other family members, or to a genetic predisposition to nail biting.[1,2,3,4,6,13,14] Of interest, nail biting is more prevalent among children whose parents were nail biters, even when parents reported ceasing the habit before their children were born.[4,14]
Onychophagia can sometimes affect individuals who are psychologically stable, but it is usually a sign of loss of control over difficult tasks.[4,5,6,14,15] The principal psychological factors found to be associated with this behavior are stress, nervousness, anxiety, and low mood.[1,2,3,4,5,6,7,13,14,15,16] In fact, nail biting was shown to be a coping mechanism in stressful conditions, and patients whose nail biting may be described as an addiction may experience more distress when trying to refrain from onychophagia.[1,3,4,6,7,10,15] On the other hand, a lack of stimulation (low activity, boredom) may also trigger or exacerbate nail biting.[1,5,7,15,16] Hunger and low self-esteem are also known to be possible causes for this oral habit.[7,15]
Onychophagia is thought to be an automatic, unintentional behavior. In adulthood, researchers suspect that alternatives to nail biting are smoking and chewing gum. One theory is that onychophagia is a continuation of the habit of thumb sucking.[2,3,14]
Psychiatric Disorders Associated With Nail Biting
In most cases, onychophagia is isolated and considered to be only a cosmetic problem. However, when co-occurring are conditions present, they are usually psychiatric in origin. At least one comorbid psychiatric disorder was present in more than two thirds of children referred to a psychiatry clinic who were nail biters, and more than one half of the parents of those children had at least one psychiatric illness, especially major depressive disorder.[5,6] However, in one study, no link between the frequency or age of onset of onychophagia and psychiatric illness was found.
The mental illnesses most commonly reported in association with nail biting in children and adolescents presenting to a mental healthcare clinic are attention-deficit/hyperactivity disorder (74%), oppositional defiant disorder (36%), and separation anxiety disorder (20%), followed by enuresis (15%), tic disorder (12%), obsessive-compulsive disorder (11%), mental retardation (9%), and major depressive disorder (6%).[1,5,6]Generalized anxiety disorder and panic disorder have also been reported. Onychophagia was documented in more than one fourth of children and adolescents with Tourette syndrome. Finally, stereotypical behaviors, such as lip biting, head banging, skin picking, and hair pulling (trichotillomania), were found in more than 60% of nail-biting children.[2,5,6,10]
Complications of Nail Biting
In most cases, the complications of onychophagia are exclusively cosmetic.[4,7,10] However, if severe, nail biting can affect a patient's quality of life. Socially, nail biting is considered an unpleasant habit that can cause humiliation, emotional suffering, and social impairment.[4,7,10,12,16]
In addition to the mental health effects, onychophagia can affect physical health. In damaging the nails, nail biting is considered a self-disfiguring behavior.[1,4,5,6,10,18] In fact, chronic nail biting can result in irreversible shortening of the nails by continually detaching the distal nail from its bed. Bleeding from around the nails can occur.[4,6,10] Moreover, onychophagia can lead to paronychia, secondary bacterial infections, and herpetic whitlow transmitted from oral herpes lesions.[2,3,4,6,7,10,18,19] Although rare, osteomyelitis of the phalanges and scarring leading to keloid formation can also occur in nail biters.[2,4]
Other physical effects of nail biting are related to the mouth and gastrointestinal tract. Severe nail biting can produce dental problems, mainly malocclusions, and small cracks in the incisors.[2,3,4,5,10,14,15] Onychophagia can harm the gingiva by causing gingivitis or abscesses.[3,5,7,20] The latter infections can be transmitted from the mouth to the nails.[3,] Nail biting can also contribute to temporomandibular disorders.[5,7,10] This habit can increase the risk for pinworm and giardia infections of the gastrointestinal tract.[13,19] Enterobacteriaceae are more likely to be present in the mouths of children who are nail biters than those who are not.[5,21]
In general, nail biting is not a worrisome condition and often resolves on its own; therefore, it may not be necessary to treat mild cases. Onychophagia is considered to be mild when nail biting is infrequent and does not lead to significant physical or social consequences. However, onychophagia associated with other comorbid disorders requires particular care.[3,5] A detailed history (including psychosocial aspects) and a thorough physical exam are important in the approach to a patient with nail biting.
The goal of management is to relieve stress and provide emotional support and motivation to help nail biters suppress the habit.[2,3] The key is that the child or teen is motivated to quit the habit.
There is agreement on the lack of long-term effectiveness of behavioral interventions for nail biting.[5,6,7,13] However, habit reversal, a cornerstone of behavioral therapy, was shown to be effective in a meta-analytic review published in 2011. The main components of habit reversal are awareness training, relaxation training, and competing response.[2,5] Decoupling, which eliminates the habit by replacing the movement with others, has been shown to be effective.
Making fun of nail biters, punishing them, or reminding them to stop biting their nails have not been shown to be effective in helping them cease the habit.[3,5,13] The efficacy of aversive therapy (applying a bad taste substance on the nails) is controversial, but it may increase anxiety.[3,5]
The following strategies may also be effective in helping individuals refrain from biting their nails:[2,3,5]
Applying olive oil to nails, which softens them and make them less appealing;
Elegantly cutting the nail edges, or manicuring the nails;
Substituting nail biting with gum chewing; and
Keeping the hands busy doing something else, such as playing music, practicing sport activities, or using balls.
Selective serotonin reuptake inhibitors are the most commonly studied medications in the management of onychophagia; these agents seem to be effective, especially in severe cases.[2,5,7,10] Clomipramine, compared with desipramine, has been found to be effective in reducing nail biting and is well tolerated by patients.[4,5,10] In a case report, lithium showed efficacy in helping a depressed patient with nail biting to overcome her chronic habit.
Another drug that may be used in the treatment of onychophagia is N-acetylcysteine, which probably works through its antioxidant effect; however, only short-term efficacy has been established.[13,23] Tranquilizers may be used to alleviate the patient's anxiety, thus reducing nail biting.
Gradual treatment to avoid the negative fallout from an excessively aggressive approach and regular follow-up visits are of great value.
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Cite this: Nail Biting: A Habit or a Disease? - Medscape - May 19, 2016.