[1] However, not all nail biting is pathological, and the difference between harmful obsession and normal behavior is not always clear.

[2] The earliest reference to nail biting as a symptom of anxiety was in the late sixteenth century in France.

[2][5] Nail biting may have an association with oral problems, such as gingival injury, and malocclusion of the anterior teeth.

[6] Nail-biting can be a source of guilt and shame feelings in the nail biter, a reduced quality of life, and increased stigmatization in the inner family circles or at a more societal level.

[2][7] Other body-focused repetitive behaviors include onychotillomania (nail picking), excoriation disorder (skin picking), dermatophagia (skin biting), and trichotillomania (the urge to pull out hair), and all of them tend to coexist with nail biting.

[2][8] As an oral parafunctional activity, it is also associated with bruxism (tooth clenching and grinding), and other habits such as pen chewing and cheek biting.

[17] More recently, technology companies have begun producing wearable devices and smart watch applications that track the position of users' hands but no research has been published so far.

[19] A small double-blind randomized clinical trial in children and adolescents indicated that N-acetylcysteine, a glutathione and glutamate modulator, could, in the short term only, be more effective than placebo in decreasing the nail-biting behavior.

[2] It may be under-recognized since individuals tend to deny or be ignorant of its negative consequences, complicating its diagnosis.