Table 2

Association of onset age of nail biting by the psychiatric disorders

Disorder
Mean age of onset
Significance*

With ADHD (n = 46)
6.2
U = 267.5, N1 = 46, N2 = 16, p = 0.1
Without ADHD(n = 16)
5.3

With ODD(n = 23)
5.2
U = 383.5, N1 = 39, N2 = 23, p = 0.3
Without ODD(n = 39)
6.4

With CD(n = 4)
4.7
U = 96.0, N1 = 58, N2 = 4, p = 0.5
Without CD(n = 58)
6

With Tic(n = 8)
6.4
U = 188.5, N1 = 8, N2 = 54, p = 0.5
Without Tic(n = 45)
5.9

With MDD(n = 4)
11.4
U = 188.5, N1 = 4, N2 = 54, p = 0.5
Without MDD(n = 58)
5.6

With SAD(n = 12)
5.5
U = 53.5, N1 = 12, N2 = 50, p = 0.07
Without SAD(n = 50)
6.0

With Enuresis(n = 10)
4.9
U = 222.0, N1 = 10, N2 = 52, p = 0.4
Without Enuresis(n = 52)
6.1

With OCD(n = 7)
6.7
U = 158.0, N1 = 7, N2 = 55, p = 0.4
Without OCD(n = 55)
5.8

With PDD(n = 2)
7.0
U = 44.0, N1 = 2, N2 = 60, p = 0.5
Without PDD(n = 60)
5.9

With MR(n = 6)
5.5
U = 124.0, N1 = 6, N2 = 56, p = 0.3
Without MR(n = 56)
6.0


ADHD = Attention deficit hyperactivity disorder, ODD = Oppositional defiant disorder, CD = Conduct disorder, MDD = Major depressive disorder, SAD = Separation anxiety disorder, MR = Mental retardation, OCD = Obsessive compulsive disorder, PDD = Pervasive developmental disorder

* Mann-Whitney U test.

Ghanizadeh Child and Adolescent Psychiatry and Mental Health 2008 2:13   doi:10.1186/1753-2000-2-13