Biting nails: children and adolescents do it especially (according to some research, this is a habit shared by 20-30% of children who go to school and 45% of teenagers); from the age of 18, this behaviour decreases although it can persist into adulthood (or begin).
Specifically, nail-biting develops in four phases: In the first, the eye falls somehow on the finger or, that finger and the nail are "perceived" (for example, thanks to the rubbing of the fingers together, or to the passage of the fingertips). In practice: attention is called in a way that is not predetermined, not programmed.
In the second stage, that finger is placed near the mouth, in contact with the lips. A gesture that is a little comforting and a little reassuring. At that point - and the third step begins - the position of the jaw is changed and the nail is quickly tapped against the front teeth with small biting actions, mostly rapid and spasmodic. Finally, the last step: the fingers are removed from the mouth.
The consequences of nail-biting, as science defines "nail-biting", do not only concern the aesthetic appearance of the finger and nail, including cuticles, but also the health and well-being of the mouth: based on the intensity and the frequency of the behaviour can, in fact, create problems with chewing, consequent to the modification of the structure of the teeth and jaw. Small imperceptible variations which, however, then make the difference.
From research in psychology and from observations, particularly in psychosomatics, it clearly emerges that teasing, biting, biting one's nails is, for many, a sort of anti-tension "strategy" . Children do this in times of distress when they don't know a lesson at school or while reading sad stories, listening to horror stories, watching television or talking on the phone. It can also be a learned behaviour from family members or, even, the consequence of a bad relationship with a mother in an unwelcoming or aggressive way.
The reasons for adults are not very different: it becomes an automatic way to discharge emotional discomfort and stress of various kinds and intensity. For example, among the most avid "nail eaters" are the " perfectionists" : for them, impatient, goal-driven and with a high level of expectation, it becomes a way to ease the inevitable frustrations and disappointments. Even feel alone, especially in the most sensitive people, can induce this habit that on the one hand download the emotional discomfort and the other is an act of self-aggression.
According to more recent studies, it could be an inherited behaviour: in fact, it is often a modality chosen by those who had at least one parent who was onychophagia for a certain period (even if he stopped before the birth of the child!).
It is also important to know that, in some cases, the frequency and severity of the behaviour make it a real disorder: in DSM 5, onychophagy is part of the obsessive-compulsive picture; it is made up of unwanted, continuous thoughts and compulsions, ie behaviours carried out not by choice but by a very strong, “irresistible” impulse to carry them out.
Whatever the age of the nail biter, no punishment is needed to eliminate this behaviour; attention to aesthetics can work (especially with adults) but alone it can almost never suffice. Counterproductive are the "threats", playing with irony or derision.
Even the various bitter glazes that should act as a disgusting deterrent as soon as you put your finger in your mouth can really help only those who are willing to change. The most correct approach is the holistic one: get to the cause, identify the reason why this sort of self-aggression is acting.
By working on these aspects, taking care of them in a conscious and pro-active way, on the one hand it will be possible to reduce or eliminate the causes, on the other hand, it will be possible to build an authentic motivation that will accompany, effectively, all the more technical interventions or strategies (such as bitter-tasting nail polish) that are useful or necessary.