. Author manuscript; available in PMC: 2015 Aug 3.

Published in final edited form as: J Abnorm Psychol. 2013 Jul 8;122(3):842–853. doi: 10.1037/a0033079

Table 3.

Birth weight as a predictor of disruptive disorder symptoms

Symptoms	Georgia Sample			Tennessee Sample			Combined Samples
Symptoms	Wald χ²	R²	p	Wald χ²	R²	p	R²	p
Inattention	7.80	.010	0.003	10.26	.005	.001	.006	<0.001
Hyp.-Imp.	2.24	.003	0.067	12.21	.006	<.001	.005	<0.001
ODD	.99	.001	0.160	1.95	.001	0.082	.001	.044
CD	3.41	.004	0.033	.885	<.001	0.174	.001	.038
Externalizing	2.17	.003	0.07	13.98	.007	<.001	.006	<0.001

Notes: All Wald χ² and R² values presented are estimates of the unique effects of birth weight on each symptom dimension adjusted for covariates. Critical value of p < .05, one-tailed; Hyp-Imp indicates hyperactive-impulsive symptoms; ODD indicates Oppositional Defiant Disorder symptoms; CD indicates Conduct Disorder symptoms; Externalizing indicates the sum of inattentive, hyperactive-impulsive, Oppositional Defiant Disorder, and Conduct Disorder symptom z-scores. Predictors and covariates included in each model were as follows: age, sex, mother’s age at the twins’ birth, gestational age, family income, and birth weight.