If the problem of nail biting occurs in adults, it may be caused by the following reasons: first, anxiety disorder, anxiety disorder patients are prone to nervousness and anxiety, worry and other emotional manifestations, but also accompanied by increased movements and behavioral manifestations, such as expressions of anxiety, fear, constantly walking around, and constantly rubbing their hands, rubbing their faces, picking their hands, biting their fingernails, etc., by biting their nails and other actions to relieve internal anxiety and tension. Secondly, OCD, the core problem of OCD is also anxiety. Patients with OCD have some special forms of expression, such as repeatedly focusing on their face, thinking their face is deformed, repeatedly picking their hands, picking the skin off their hands, repeatedly plucking their hair, such as pulling their hair out, or possibly repeatedly biting their hands, biting their nails to the point of baldness and bleeding, etc. These also belong to the special OCD These also belong to one of the special types of OCD. Thirdly, bad habits, some people may have developed the bad habit of biting their nails since childhood, and have been doing so since childhood.