Onychotillomania, or nail-picking disorder, is a common and under-recognized disorder defined as self-induced trauma to the nail unit. The trauma may be caused by repeatedly rubbing the nail fold (habit tic deformity) or using instruments such as scissors, knives, or razor blades. Onychotillomania presents with characteristic or bizarre morphologies of the nail plate and damage to the nail bed and periungual skin depending on the type of self-destructive behaviors employed by the patient.

Patients may have insight into the self-induced nature of their disorder, or they may completely deny any involvement.

The condition has been associated with psychiatric disorders including obsessive-compulsive disorder, a specific phobia, body dysmorphic disorder, impulse control disorder, a delusional disorder, depression, or suicidal ideation. Onychotillomania may be one form of self-mutilating behavior seen in the Lesch-Nyhan and Smith-Magenis syndromes.

While data is sparse, there may be a slight female predominance. Age of onset is late childhood or early adolescence.