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. Author manuscript; available in PMC: 2016 Nov 1.
Published in final edited form as: Behav Genet. 2015 Oct 14;45(6):622–634. doi: 10.1007/s10519-015-9756-0

Figure 2.

Figure 2

Generic ML-SEM genetic simplex model. Biometric components of Pit, phenotypic CES-D scores for twin i at time t, are estimated between- and within-families; Atb = between-family genetic effect at time t; Etb = between-family (common) environmental effect at time t; Atw = within-family genetic effect at time t; Etw = within-family (nonshared) environmental effect at time t; uAtb = unique between-family genetic effect at time t; uEtb = unique between-family environmental effect at time t; uAtw = unique within-family genetic effect at time t; uEtw = unique within-family environmental effect at time t; aar, car, and ear = auto-regression coefficient between adjacent components; the between-family and within-family genetic loadings for the MZ twins are 1 and 0, respectively, to meet the assumption that MZ twins share 100% of their genes; the between-family and within-family genetic loadings for the DZ twins are both √5 to meet the assumption that DZ twins share 50%, on average, of their segregating genes.