Table 5.

Parameter estimates of multilevel models predicting offspring alcohol use disorder (AUD) symptom counts from AUD symptom counts in the twin parent or twin pair.

	Model 1		Model 2		Model 3		Model 4		Model 5		Model 6
Parameter	b	SE	b	SE	b	SE	b	SE	b	SE	b	SE
Random effects (variance components)
Twin family level (3)	.07*	.03	.06*	.03	.06*	.03	.06*	.03	.06*	.03	.06*	.03
Nuclear family level (2)	.21*	.04	.20*	.03	.19*	.03	.20*	.03	.20*	.03	.19*	.03
Offspring level (1)	.60*	.02	.54*	.02	.54*	.02	.54*	.02	.54*	.02	.54*	.02
Fixed effects
Twin pair AUD
Parent AUD (level 2)			.14*	.02	.09*	.03
Between twin families (level 3)							.18*	.03	.18*	.03	.13*	.04
Within twin families (level 2)							.06	.04
MZ within twin families (level 2)									.07	.07	.05	.07
DZ-MZ within twin families (level 2)									−.01	.08	−.02	.08
Spouse AUD (level 2)			.14*	.03	.14*	.03	.14*	.03	.14*	.03	.14*	.03
Offspring covariates (level 1)
Sex			.45*	.04	.46*	.04	.45*	.04	.45*	.04	.46*	.04
Age			.20*	.04	.20*	.04	.20*	.04	.20*	.04	.20*	.04
Age2			−.004*	<.001	−.004*	<.001	−.004*	<.001	−.004*	<.001	−.004*	<.001
Twin Covariatesa (level 2)
Cigarette use					.13*	.05					.13*	.05
History of conduct disorder symptoms					.08*	.02					.08*	.02
Spouse Covariatesa (level 2)
Age at first child					−.01*	.006					−.01*	.006

Note: Parameters are unstandardized. Parental and offspring symptom counts are distributed as z-scores. The parameters were weighted to produce estimates from the entire Australian Twin Registry cohort, and the standard errors reflect the clustered nature of the data.

^aOnly covariates with significant unique effects are shown; the covariates included for both twins and spouses were: educational attainment, age at the birth of their first child, frequency of church attendance, divorce, use of cigarettes, use of any illegal substances, conduct disorder symptoms, symptoms of major depression, suicidality. See Table 2 for an explanation of the models.