. Author manuscript; available in PMC: 2013 Aug 1.

Published in final edited form as: J Child Psychol Psychiatry. 2012 Feb 10;53(8):864–873. doi: 10.1111/j.1469-7610.2012.02527.x

Table 1.

Means (and standard deviations) for gender, age, IQ, and reading difficulties questionnaire (RDQ) in ADHD probands, siblings of ADHD probands and unaffected controls.

		ADHD Probands (n=630)	ADHD siblings			Controls (n=485)	F / χ2	p
		ADHD Probands (n=630)	Affected (n=84)	Subthreshold (n=77)	Unaffected (n=513)	Controls (n=485)	F / χ2	p
Male %		88	71	57	47
Age		11.46 (2.69)	11.06 (3.10)	11.53 (2.74)	11.77 (3.25)	12.11 (2.76)	7.09	0.01
IQ		100.64 (14.74)	99.78 (14.11)	98.13 (14.12)	104.04 (13.86)	107.13 (12.17)	29.32	0.01
RDQ		16.33 (7.55)	15.53 (8.14)	14.95 (7.44)	10.36 (5.99)	9.86 (5.45)	142.64	0.01
Centre groups %	a	53	71	49	48	49
	b	27	21	27	28	51
	c	8	2	18	11	0	163.38	0.01
	d	12	6	6	13	0

a= Netherlands

b= UK- London

c= UK- Southampton

d= Spain