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Nail biting is a very common habit that mostly affects kids but it can be present in adults and older people too. about it is manifested by biting one's fingernails or toenails during periods of nervousness, stress or boredom.

It can be a sign of mental or emotional disorder but is commonly seen in intellectuals. The medical term for nail biting is chronic onychophagia. It belongs to the group of disorders called Stereotypic movement disorders. Often starting in childhood, nail biting can persist in some adults and become an irritating and unsightly nuisance. Some nail biters experience the habit with such severity that their nails are constantly bitten down to the maximum and bleeding, causing pain and often embarrassment.


Several studies have shown that approximately 28% to 33% of children ages 7-10 are biting their nails, as well as the 44% of adolescents, 19% to 29% of young adults and 5% of older adults. It is more common in boys. Stereotypic movements are common even in infants and toddlers. Some estimates suggest that 15–20 percent of children under age three exhibit some kind of rhythmic, repetitive movements.

What is stereotypic movement disorder?

Stereotypic movements are described as a special psychiatric symptom, since they have symptoms of both psychotic and neurological disorders. They may also arise from unexplained causes.

These movements may include:

* head banging

* nail biting

* playing with hair 

* thumb sucking

* hand flapping

* nose picking

* whirling

* body rocking

* picking at the body

* self-biting

* object biting

* self-hitting

* compulsive scratching

* eye gouging

* teeth grinding (bruxism)

* breath holding

* stereotyped sound production

The exact definition is that these disorders include movements that cause physical harm or severely interfere with normal activities. Although many think that it happens only to kids, this isn't true at all. Stereotypic movements occur in people of any age, including the very young, but they are most prevalent in adolescence.
People may experience one particular stereotyped movement or even several of them. The exact mechanisms and triggers are still unknown, but they seem to increase with boredom, tension, or frustration, and it appears that the movements are self-stimulatory and sometimes pleasurable.


Similar to stereotypic movements, a habit is a learned behavior that a person repeats so often that he or she begins to do it without even thinking about it. Certain habits can be helpful but some may seem to serve no particular purpose.

  1. Helpful habits - brushing teeth before going to bed or buckling your seatbelt when getting into a car.
  2. Habits with no purpose - hair twirling, thumb sucking, nail biting… etc.

Some habits are annoying, and some can cause distress or become the focus of teasing. Still others may have harmful effects. For example, thumb sucking, which can go on for years, can cause dental problems.

Is there a thing called ’’Physiological habit’’?

Some habit-like behavior is normal for a developing child. For example, approximately one half of all 2-year-old children engage in thumb sucking. However, if this behavior persists through childhood, the likelihood of it becoming a substantial problem may increase with age.

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