or other family members may be helping to perpetuate the problem. For example, punishments have been shown to be not better than placebo, and in some cases may even increase the nail biting frequency. Epidemiology While it is rare before the age of 3, about 30 percent of children between 7 and 10 years of age and 45 percent of teenagers engage in nail biting. Finally, prevalence decreases in adults. Figures may vary between studies, and could be related to geographic and cultural differences. The proportion of subjects that have ever had the habit (lifetime prevalence) may be much higher than the proportion of current nail-biters (time-point prevalence). Although there does not seem to be a gender correlation, results of epidemiological studies on this issue are not fully consistent. It may be underrecognized since individuals tend to deny or be ignorant of its negative consequences, complicating its diagnosis. Having a parent with a mental disorder is also a risk factor. References External links Body-focused repetitive behavior Conditions of the skin appendages Fingers Habit and impulse disorders Nails (anatomy) Neurocutaneous conditions Pica (disorder)