Table 3.

Parameter estimates and confidence intervals (CD for twin studies of alcohol use disorders

		Heritability		Shared environment		Unique environment
Relationship	Study	Estimate	95% CI	Estimate	95% CI	Estimate	95% CI
	All twins	0.510	0.448–0.556	0.095a	0.033–0.158	0.393	0.375–0.415
Male twins	All males	0.516	0.447–0.567	0.083a	0.015–0.149	0.391a	0.367–0.417
	Kaij (1960)	0.402	0.153–0.646	0.481	0.261–0.673	0.118	0.060–0.210
	Gurling et al. (1984)	0.004	0.000–0.777	0.690	0.003–0.843	0.306	0.115–0.526
	Allgulander et al. (1991)	0.161	0.000–0.630	0.263	0.000–0.508	0.576	0.368–0.777
	Caldwell & Gottesman (1991), Romanov et al. (1991)	0.772	0.242–0.937	0.000	0.000–0.456	0.228	0.063–0.560
	McGue et al. (1992)	0.585	0.021–0.950	0.275	0.000–0.734	0.140	0.047–0.328
	Reed et al. (1996)	0.597	0.463–0.648	0.000	0.000–0.107	0.403	0.352–0.458
	Heath et al. (1997)	0.675	0.379–0.779	0.002	0.000–0.246	0.323	0.221–0.450
	Kendler et al. (1997)	0.529	0.384–0.671	0.133	0.019–0.245	0.338	0.289–0.391
	True et al. (1999)	0.510	0.277–0.621	0.044	0.000–0.240	0.446	0.379–0.519
	Prescott et al. (1999)	0.489	0.294–0.578	0.000	0.000–0.156	0.511	0.422–0.609
	Knopik et al. (2004)	0.599	0.288–0.694	0.000	0.000–0.260	0.401	0.306–0.511
	Magnusson et al. (2012)	0.335	0.000–0.573	0.104	0.000–0.431	0.561	0.427–0.714
Female twins	All females	0.441	0.246–0.605	0.158	0.000–0.327	0.400	0.347–0.455
	Gurling et al. (1984)	0.000	0.000–0.777	0.693	0.003–0.843	0.307	0.115–0.526
	Allgulander et al. (1991)	0.229	0.000–0.818	0.383	0.000–0.720	0.388	0.173–0.672
	Caldwell & Gottesman (1991)	0.091	0.000–0.876	0.652	0.000–0.868	0.257	0.069–0.523
	McGue et al. (1992)	0.000	0.000–0.904	0.626	0.000–0.881	0.374	0.081–0.814
	Heath et al. (1997)	0.603	0.112–0.738	0.007	0.000–0.435	0.390	0.262–0.553
	Prescott et al. (1999)	0.591	0.189–0.706	0.001	0.000–0.343	0.409	0.294–0.545
	Knopik et al. (2004)	0.529	0.130–0.649	0.015	0.000–0.357	0.456	0.351–0.578
	Magnusson et al. (2012)	0.404	0.024–0.705	0.205	0.000–0.523	0.390	0.289–0.511
Male and female twins	Romanov et al. (1991)	0.385	0.000–0.721	0.165	0.000–0.491	0.449	0.279–0.668

^aParameter has significant heterogeneity.