Adult nail gnawing may be caused by the following reasons: 1, from childhood there are bad behavior habits, when the problem of fingernail biting in childhood, especially in the weaning of finger nail biting, nibbling finger nails, at that time did not solve, parents did not stop in time then this behavior, it is easy to continue down, and finally to adulthood did not disappear, moving to nail gnawing; 2, mental illness If the patient has repeatedly chewed nails, nails will gnaw bald, bleeding can not be stopped, it may be very serious obsessive-compulsive behavior; 3, physical disease, especially endocrine abnormalities or lack of certain trace elements in the body, etc., but also in combination with the emergence of personality problems. Or social pressure to make themselves particularly nervous, anxious, it is easy to chew the nails of the problem.