Prevalence of nail biting and its association with mental health in a community sample of children.

Background: This study evaluates onychophagia or nail biting (NB) prevalence and association with mental health of a community sample of children from Shiraz, Iran.

Findings: The parents of 743 primary school children, selected by random sampling, reported NB behavior of their children and themselves. Children's mental health problem was assessed using the Strengths and Difficulties Questionnaire (SDQ). 22.3% (95% CI: 19.3 to 25.3) of children had NB behavior in the last three months (girls: 20.1% (95% CI: 15.9 to 24.2). The rate in boys was 24.4% (95% CI: 20.1 to 28.7). 36.8% of the children with NB had at least one family member with nail biting. Older age was associated with a higher prevalence of NB while a higher score on the prosocial score was associated with a lower prevalence of NB.

Conclusions: NB is a very common behavior in both genders in children and their family members. Children with NB have less prosocial ability than those without it.