Table 2.

Age of onset for nail biting and tics among patients with Tourette syndrome

	All patients with TS			Boys with TS			Girls with TS
	ADHD	Non-ADHD	P	ADHD	Non-ADHD	P	ADHD	Non-ADHD	P
n	176	359		157	287		19	72
Sex			0.008*
Boys	157 (89.2)	287 (79.9)
Girls	19 (10.8)	72 (20.1)
Age			0.085			0.109			0.947
4–6 years	15 (8.5)	53 (14.8)		12 (7.6)	40 (13.9)		3 (15.8)	13 (18.1)
7–12 years	143 (81.3)	256 (71.3)		128 (81.5)	206 (71.8)		15 (78.9)	50 (69.4)
13–15 years	12 (6.8)	37 (10.3)		11 (7.0)	30 (10.5)		1 (5.3)	7 (9.7)
16–18 years	6 (3.4)	13 (3.6)		6 (3.8)	11 (3.8)		0 (0)	2 (2.8)
Nail biting			< 0.001*			< 0.001*			0.002*
With	132 (75.0)	171 (47.6)		115 (73.2)	135 (47.0)		17 (89.5)	36 (50.0)
Without	44 (25.0)	188 (52.4)		42 (26.8)	152 (53.0)		2 (10.5)	36 (50.0)
Starting age for nail biting	5.3±2.5†	3.8±3.0†	< 0.001*	5.3±2.6†	3.8±3.0†	< 0.001*	5.3±1.9	3.6±2.9†	0.023*
Starting age for tics	6.6±1.8	6.2±2.0	0.007*	6.7±1.8	6.3±2.0	0.008*	5.8±1.7	5.8±2.0	0.891
Sequence of nail biting			0.902			0.8			0.693
Same as tics	31 (23.5)	38 (22.4)		27 (23.5)	30 (22.4)		4 (23.5)	8 (22.2)
Before tics	75 (56.8)	95 (55.9)		68 (59.1)	76 (56.7)		7 (41.2)	19 (52.8)
After tics	26 (19.7)	37 (21.8)		20 (17.4)	28 (20.9)		6 (35.3)	9 (25.0)

Data are expressed as n (%) for age, sex and nail biting.

*Significant difference between ADHD and non-ADHD.

†Significant compared with starting age of tics as tested by proportional odds ordinal logistic regression models.

ADHD, attention deficit hyperactivity disorder; TS, Tourette syndrome.;.