Table 1A.

Standardized Differences Between Alcohol Exposed and Non-exposed Groups in the Means of Propensity Score Model Covariate at Target Age 11 (Intake Assessment)

		Full sample		Estimates with twin pairs discordant on exposure
Individual level variables		Unweighted sample	Weighted sample	All twins	MZ twins	DZ twins
1	Twin IQ	−0.09	0.00	0.09	0.12	0.06
2	Twin menarche1	0.10	0.01	−0.04	−0.02	−0.09
3	Twin puberty measure	0.25	0.01	0.07	0.03	0.13
4	Twin GPA	−0.21	−0.02	0.05	0.02	0.11
5	Twin academic problems	0.31	0.01	0.10	0.13	0.05
6	Twin academic motivation	−0.38	−0.01	−0.10	−0.04	−0.18
7	Twin externalizing disorder symptoms	0.33	0.00	0.20	0.19	0.21
8	Twin delinquent behaviors	0.51	0.04	0.06	0.05	0.05
9	Conflict between twin and parents	0.29	0.01	0.05	0.09	−0.02
	Absolute mean of individual level variables	0.27	0.01	0.08	0.08	0.10
Family level variables
10	Twin sex2	−0.13	−0.03
11	Twin age	0.28	0.02
12	Twin ethnicity3	0.15	0.00
13	Parent age	0.00	−0.02
14	Parent IQ	−0.15	−0.04
15	Parent years of education	−0.21	−0.01
16	Parent occupational status	−0.14	−0.01
17	Family income	−0.09	−0.02
18	Family history of externalizing	0.14	0.01
19	Parent delinquent behaviors	0.32	0.04
20	Parent externalizing disorder symptoms	0.29	0.02
21	Parent alcohol abuse or dependence symptoms	0.21	0.03
22	Parent drug abuse or dependence symptoms	0.24	0.05
23	Parent alcohol use quantity and frequency index	0.39	0.04
24	Parent tobacco use quantity and frequency index	0.45	0.03
25	Parent ever used marijuana	0.25	0.07
26	Parent number of times used marijuana	0.24	0.06
27	Parent number of drug classes ever used	0.30	0.06
28	Parents ever separated or divorced	0.24	0.01
29	Immediate family member of twins ever died	0.05	−0.01
	Absolute mean of all variables	0.23	0.03

Positive standardized differences indicate that the value of a covariate was higher, on average, among early-exposed participants than those without early exposure, while negative standardized differences indicate that the value of a covariate was higher among those without early exposure to alcohol than those who experienced early exposure. Values in bold indicate standardized differences greater than 0.25. The “weighted sample” is the sample after application of the propensity score as sample weights, as described in text. Standardized difference is calculated as (M_exposed – Mn_onexposed) / √[(σ²_exposed + σ²_nonexposed) /2] . ¹ Applies to females only, variable is a binary indicator of menarche status. ² Sex is coded Male = 0, Female = 1. ³ Ethnicity coded White = 0, Any other ethnicity = 1.