This study of children and adolescents presenting at a mental healthcare clinic showed that 65% of children with nail biting had at least one of the other stereotypic behaviors. More than two-thirds of children who have NB who are referred to a mental health clinic are also suffering from at least one major co-morbid psychiatric disorder. Two-thirds of the interviewed parents were also suffering from at least one major psychiatric disorder, especially MDD. Unfortunately, no study about the co-morbidity of psychiatric disorders in children with NB, co-morbidity of NB in children with psychiatric disorders, or any study about the prevalence of psychiatric disorders concerning parents of children with NB were found to compare with the current results.
The results of this study do not appear to support previous studies which report that onychophagia is a sign of anxiety or that anxiety and nervousness are etiological factors for onychophagia [7, 13, 14]. Also, these results are not consistent with the study that concluded that onychophagia does not reflect any underlying emotional disturbance . A possible explanation of this lack of consistency is that children and adolescents with psychiatric disorders who also have NB may not be typical of children and adolescents in the community who have NB.
Nail biting is considered by some to be a variant of normal tactile and environmental exploration. However, it should be noted that this behavior causes physical damage and distress as well as a motivation to change, and therefore cannot be considered benign in children. NB is usually associated with psychiatric disorders in this clinical sample. One explanation is that although NB might be associated with anxiety and functions as a tension reduction behavior, this tension and anxiety may be secondary to another psychiatric disorder such as ADHD and its consequences. Affected patients are aware of their habit and admit their continual nail biting, but they seem unable to control it. It is not possible to determine whether the presence of co-morbid psychiatric disorders is a cause or a consequence of NB.
Onychophagia is reported to be a difficult behavior to modify and the treatment results are not as impressive as initially reported . Furthermore, research has shown that drugs are not effective for treatment of nail biting and habit reversal techniques are not effective in the long term . It is possible that low rates of success in treatment might be related to lack of sufficient knowledge about the co-morbidity of psychiatric disorders in children with NB or psychiatric disorders in their parents, and therefore the lack of sufficient resources directed to dealing with underlying causes or maintaining factors. One suggestion would be that future interventional studies on NB should be conducted with special attention to identifying and addressing any psychiatric disorders in these children or adolescents and their parents. This way, it can be determined if treating co-morbid psychiatric disorders in these cases can increase effectiveness of dealing with the NB.
The results of this study suggest that psychiatrists should look for nail biting amongst their patients who present with mental healthcare problems. NB seen in this setting may indicate anxiety. Nail biting, which causes distress to the child and adolescent, may also be an issue that can be used as a way to discuss motivation for change in general.
Care should be taken about generalization of the results because the sample size was relatively low and the participants were exclusively children and adolescents who were referred to the psychiatric clinic for different reasons, not solely for NB. Furthermore, NB duration range was at least 6 months to 15 years. It might show that children with milder forms of NB are less likely to suffer from co-morbid psychiatric disorders and are therefore not as likely to be referred to this clinic; and that this clinical sample consisted of children and adolescents with moderate or severe forms of both nail biting and psychiatric disorders. These might have been key reasons, rather than nail biting per se, for the high co-morbidity rates found in the participants and their parents. Further studies in the general population are recommended.