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. Author manuscript; available in PMC: 2010 Apr 8.
Published in final edited form as: Biol Psychiatry. 2010 Jan 1;67(1):71–77. doi: 10.1016/j.biopsych.2009.08.010

Table 3.

Polychoric correlation coefficients (r) and 95% confidence intervals (95% CI) for anorexia nervosa and bulimia nervosa

Within Trait Cross Trait
Anorexia Nervosa Bulimia Nervosa Within Twin Cross Twin
Zygosity N* Concordant/
Discordant
Pairs** 		r
(95% CI)		 N* Concordant
/Discordant
Pairs** 		r
(95% CI)		 N* Concordant
/Discordant
Pairs** 		r
(95% CI)		 N* Concordant/Di
scordant
Pairs** 		r
(95% CI)
NARROW
MZ 3874 2 / 22 .58
(.29, .87)		 3928 6 / 38 .65
(.45, .85)		 4071 3 / 71 .39
(.15, .63)		 3874 1 / 58 .15
(−.22, .52)
DZ 2768 0 / 12 NE† 2776 0 / 26 NE† 2896 2 / 35 .51
(.22, .80)		 2766 0 / 36 NE†
BROAD
MZ 3852 9 / 120 .34
(.16, .48)		 3928 15 / 78 .63
(.49, .77)		 4058 29 / 200 .54
(.44, .64)		 3852 13 / 174 .27
(.11, .43)
DZ 2730 0 / 85 NE† 2774 2 / 70 .15
(−.16, .46)		 2877 21 / 122 .60
(.48, .72)		 2726 1 / 128 −.21
(−.50, .08)
*

N = number of individuals used in the calculation;

**

number of concordant pairs used in the calculation;

†

Not Estimable. Within trait correlations reflect the correlation of AN and BN between members of twin pairs by zygosity group. Cross trait-within twin correlations reflect the correlation between AN and BN within individuals. Cross trait-cross-twin correlations reflect the correlations of AN in one twin with BN in the co-twin across zygosity groups.