Table 6.

Parameter estimates and 95% confidence intervals (CI) for adoption studies^a

Relationship	Study	Heritability estimate	95% (CI)
Summary	All offspring	0.356	0.216 to 0.499
	Male offspring	0.400	0.235 to 0.562
	Female offspring	0.241	−0.045 to 0.517
Mother/son	Cloninger et al. (1981)	0.166	−0.100 to 0.738
	Sigvardsson et al. (1996)	0.210	−0.062 to 0.865
Father/son	Cloninger et al. (1981)	0.172	0.092 to 0.588
	Sigvardsson et al. (1996)	0.181	−0.005 to 0.711
Parent/son	Cadoret et al. (1987)	0.504	0.222 to 1.555
	Goodwin et al. (1973)	0.392	−0.061 to 1.426
Mother/daughter	Bohman et al. (1981)	0.287	0.053 to 1.034
	Sigvardsson et al. (1996)	−0.630	−1.800 to 1.249
Father/daughter	Bohman et al. (1981)	0.062	−0.276 to 0.513
	Sigvardsson et al. (1996)	−0.031	−0.889 to 0.736
Parent/daughter	Goodwin et al. (1977)	0.200	−0.796 to 1.388

^aThe heritability estimate for the adoption studies was estimated by doubling the correlation between the biological parents and offspring (in the same way that the genetic correlation between dizygotic twins is half the genetic correlation of monozygotic twins). Accordingly, the theoretical limits of the confidence intervals is −2 and 2 rather than −1 and 1.