Table 3.

GCTA Estimates of SNP Heritability for Startle Indices

	Threshold
	.025	.050	.100	None
Overall startle
Unweighted	.493 (.223)	.429 (.219)	.373 (.218)	.526 (.025)
Weighted	.493 (.283)	.526 (.279)	.505 (.279)	—
Family C	—	—	—	.498 (.052)
Aversive difference
Unweighted	.000 (.213)	.000 (.208)	.000 (.207)	.108 (.031)
Weighted	.008 (.278)	.000 (.271)	.000 (.269)	—
Family C	—	—	—	.118 (.061)
Pleasant difference
Unweighted	.001 (.213)	.000 (.209)	.000 (.206)	.047 (.031)
Weighted	.062 (.274)	.000 (.270)	.000 (.267)	—
Family C	—	—	—	.048 (.062)

Note. Threshold refers to the genetic relatedness threshold used for selecting unrelated individuals. None indicates that no threshold was imposed and all subjects were included. Unweighted GRM is the raw GRM, whereas Weighted GRM uses weights based on LD patterns to discount those SNPs in high LD (Speed et al., 2012). This is not used in the full sample, because the method was designed for samples of unrelated individuals or samples containing a small number of large pedigrees (Doug Speed, e-mail communication, May 4, 2014). Family C uses all subjects while simultaneously modeling shared environmental influences. Sample sizes for the different GRM cutoffs for unrelated people ranged from 1,640 to 1,677 for the unweighted estimates and from 1,353 to 1,396 for the weighted estimates. For the full sample, it was 3,321 to 3,323. GCTA = genome-wise complex trait analysis; SNP = single nucleotide polymorphism; GRM = genetic relationship matrix; LD = linkage disequilibrium