Table 1.

Detailed family structure of the QTIM and HCP samples

			QTIM	HCP
Total sample size (individuals) for phenotypic analysis			834	890
Final sample size (individuals) for twin modeling			833^*	853**‡
Incl.	N complete trios		23	184
	Incl.	N MZ pairs + one sibling	9	75
		N DZ pairs + one sibling	14	71
		N sibling trios	0	38
	N complete pairs		275	109
	Incl.	N MZ pairs	101	14
		N DZ pairs	142	19
		N twin-sib pairs	32	38
		N sibling pairs	0	38
	N singletons		214	83
	Incl.	N twins	181	33
		N non-twin siblings	33	50

↵* One individual from a family of four siblings was excluded for twin modeling, i.e., maximum family size restricted to three individuals (twin and/or non-twin siblings).
** Thirty-seven individuals from families with more than four siblings were excluded with no effect on the sample characteristics (mean age 28, SD = 3.7, range 22–37, 56.5% females after exclusion).
‡ To maximize the HCP sample, 12 half-siblings were included (categorized as siblings in twin analysis); this low number should not affect estimates from twin modeling.