Table 4.

Estimates of variance components from univariate twin models of blackout and passing out.

	Women			Men			Constrained across Sex
	A	C	E	A	C	E	A	C	E
Lifetime blackout
occurrence	.20 [0 – .56]	.17 [0 –.48]	.64 [.50 – .78]	.53 [.35 – .71]	0	.47 [.29 – .65]	.43 [.32 – .54]	0	.57 [.45 – .68]
susceptibilitya	.16 [0 – .45]	.02 [0 – .26]	.83 [.73 – .92]	.27 [.15 – .40]	0	.73 [.60 – .86]	.21 [.13 – .28]	0	.79 [.72 – .87]
Lifetime passing out
occurrenceb	0	.29 [.17 – .41]	.72 [.60 – .83]	.32 [.09 – .55]	0	.68 [.46 – .91]	__	__	__
susceptibilitya	0	.15 [.08 – .22]	.85 [.78 – .92]	.15 [.01 – .29]	0	.85 [.71 – .99]	.06 [0 – .21]	.07 [0 – .17]	.87 [.79 – .95]

Note: A = additive genetic influences, C = shared environmental influences, E = nonshared environmental influences. Bold indicates significance.

^aanalyses controlling for the effects of frequency of intoxication.

^bconstrained results are not presented because estimates could not be constrained across sex without a significant decrease in model fit.