Table 4.

Within-pair differences in disruptive disorder phenotypes regressed on differences in birth weight

		GA Sample			TN Sample			Combined Samples
Symptoms	Predictor	t	p	R2	t	p	R2	z	p	R2
Inattention	BW	−0.52	0.30	<0.01	−2.35	0.01	<0.01	−2.40	0.009	<0.01
	Zyg.	−2.48	0.01	0.01	−0.51	0.61	<0.01
	BW X Zyg.	0.23	0.82	<0.01	0.94	0.35	<0.01	0.97	0.17	<0.01
Hyperactive-Impulsive	BW	0.09	0.54	<0.01	−2.45	0.007	<0.01	−2.10	0.02	<0.01
	Zyg.	−1.43	0.15	<0.01	−1.26	0.21	<0.01
	BW X Zyg.	0.86	0.39	0.01	1.08	0.28	<0.01	1.22	0.11	<0.01
ODD	BW	−0.26	0.40	<0.01	−0.19	0.48	<0.01	−0.29	0.39	<0.01
	Zyg.	0.34	0.74	<0.01	−0.74	0.46	<0.01
	BW X Zyg.	−0.26	0.80	<0.01	1.64	0.10	<0.01	1.56	0.12	<0.01
CD	BW	−2.43	0.008	<0.01	−0.01	0.50	<0.01	−2.27	0.01	<0.01
	Zyg.	−0.91	0.37	<0.01	0.05	0.96	<0.01
	BW X Zyg.	1.25	0.21	0.03	1.02	0.31	<0.01	1.25	0.21	<0.01
Externalizing	BW	0.43	0.66	<0.01	−1.83	0.03	<0.01	−1.47	0.07	<0.01
	Zyg.	−0.95	0.34	<0.01	−1.33	0.19	<0.01
	BW X Zyg.	0.36	0.72	<0.01	1.81	0.07	<0.01	1.84	0.07	<0.01

Notes: All values presented are adjusted for covariates. Covariates included in all models but not reported in the table include child’s age, ethnicity, gestational age, dyad sex constellation, dyad sex constellation X birth weight interactions, and log of family income. Significance is reported for main and interactive effects of birth weight only; critical value of p < .05 (one-tailed test for main effects of birth weight; two-tailed test for zygosity and birth weight X zygosity interaction); Zyg. = zygosity; CD = conduct disorder symptoms; ODD = oppositional defiant disorder symptoms; BW = birth weight; BW X zygosity = zygosity X birth weight interaction term.