Nail biting, also known as onychophagy or onychophagia, is an oral compulsive habit of biting one's fingernails. It is sometimes described as a parafunctional activity, the use of the mouth for an activity other than speaking, eating, or drinking.
Nail biting is a common habit, with it being present in approximately 20-30% of the population, and that statistic only increases to ~37% when explicitly reviewing the ages three to twenty-one year-old demographic. More pathological forms of nail biting are considered impulse control disorders in the DSM-IV-R and are classified under obsessive-compulsive and related disorders in the DSM-5. The ICD-10 classifies the practice as "other specified behavioral and emotional disorders with onset usually occurring in childhood and adolescence". However, not all nail biting is pathological, and the difference between harmful obsession and normal behavior is not always clear. The earliest reference to nail biting as a symptom of anxiety was in the late sixteenth century in France.
