1 Aggression toward themselves
Some theories say people bite their nails due to the fact that they bear inward aggression towards themselves. It may also be a form of self-mutilation.
2 A habit since childhood
Some theories suggest that nail-biting has become a habit since children grow up putting things in their mouths, and sometimes their fingers.
3 Stress, hunger or boredom
Some people bite their nails when they're anxious, stressed, bored or hungry.
4 Associated with OCD
In 2012, the American Psychiatric Association linked nail-biting to obsessive compulsive disorder.
5 A sign of perfectionism
A study has found that nail-biters tend to be perfectionists who take out their frustration or stress on their nails.
6 A learned behavior
Nail-biting may sometimes be a formed habit due to being exposed to it in families.
7 An instinctual habit
Some people believe that nail-biting is an instinct passed down to us from our early ancestors. Thus, some people resort to it when they're in need of relief.
8 An escape mechanism
Psychologists have suggested that nail-biting is a way to temporarily escape a bad situation by giving the person a distraction.
9 It feels good
Some people bite their nails merely because they enjoy the feeling of the nail coming off.