. Author manuscript; available in PMC: 2015 Apr 10.

Published in final edited form as: Psychol Med. 2013 Oct 10;44(10):2223–2229. doi: 10.1017/S0033291713002493

Table 2.

Concordance rates and tetrachoric correlations with 95% confidence intervals (95% CI) for clinical diagnosis of ADHD in 59,514 Swedish twins, by Sex and Zygosity

	MZM	DZM	MZF	DZF	Opposite-sex twins
	MZM	DZM	MZF	DZF	Case=Male	Case=Female
Clinical diagnosis of ADHD
No. of concordant affected pairs	35	13	11	5	29	29
No. discordant pairs	55	139	38	68	277	100
Concordance rates (95% CI)	0.56 (0.45–0.66)	0.16 (0.09–0.25)	0.37 (0.21–0.54)	0.13 (0.04–0.26)	0.17 (0.12–0.24)	0.37 (0.27–0.47)
Tetrachoric correlations (95% CI)	0.90 (0.84–0.94)	0.48 (0.33–0.61)	0.81 (0.68–0.90)	0.50 (0.28–0.67)	0.49 (0.40–0.58)

MZM, monozygotic male; MZF, monozygotic female; DZM, dizygotic male; DZF, dizygotic female.