Table 7.

VATSPSUD Model Fitting Results

Model		Compared to Model	Δ Fit
			Δ χ2 units	Probability	Δ DF	Δ AIC
Ia	Full Model	–	–	–	–	–
II	Sexes equated	I	9.42	0.86	45	20.58
III	C Matrix dropped	II	34.42	0.87	15	55.57
IV	A1	III	220.71	0.00	10	23.72
V	A1 + A2	III	199.32	0.00	6	47.36
VI	A1 + A2 + A3	III	185.44	0.00	3	56.44
VI	A1 + A2 + A3 + A4	III	74.08	0.05	1	58.09
VIIb	A1 + A2 + A3 + A4 + A5	III	35.96	0.90	3	60.04

AIC, Akaike’s Information Criterion; VATSPSUD, Virginia Adult Twin Study of Psychiatric and Substance Use Disorders.

^aFit of Model I: 2LL = 43147.81, df = 17540, AIC = 8067.81; All subsequent models are compared to Model I.

^bBest fit model.