Table 3.

Correlation matrix of study outcomes and relevant covariates

	4-month TL	12-month TL	18-month TL	ADHD T-score	Prenatal smoking	Infant birthweight	Sex	Race	SES	Maternal pregnancy complications
4-month TL	1
12-month TL	0.24**	1
18-month TL	0.25**	0.24**	1
ADHD T-score	− 0.02	− 0.05	− 0.05	1
Prenatal smoking	0.15	− 0.12	− 0.18*	0.13	1
Infant birthweight	− 0.04	− 0.14	0.02	0.05	− 0.17*	1
Sex	− 0.01	− 0.05	− 0.00	− 0.12	0.00	− 0.06	1
Race	0.02	− 0.21**	− 0.09	0.07	0.12	0.29****	0.05	1
SES	0.02	− 0.18*	0.02	− 0.04	− 0.17*	0.30****	0.03	0.40****	1
Pregnancy complications	− 0.05	− 0.01	− 0.02	− 0.10	− 0.08	− 0.22**	0.02	− 0.20**	− 0.09	1
Maternal postnatal depression	0.05	0.10	− 0.13	0.23**	0.26**	− 0.09	− 0.05	− 0.15	− 0.27***	0.10

Prenatal smoking: 0 = no, 1 = yes; sex: 1 = male, 2 = female; race: 0 = Black, 1 = White, 2 = other; pregnancy complications: 0 = no, 1 = yes

*p < 0.05, **p < 0.01; ***p < 0.001; ****p < 0.0001