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. Author manuscript; available in PMC: 2021 Mar 1.
Published in final edited form as: J Res Adolesc. 2019 May 16;30(1):126–141. doi: 10.1111/jora.12506

Figure 1.

Figure 1.

Illustration of a univariate ACE twin model with sibling interaction effects. A refers to latent genetic influences on phenotype of interest; C refers to latent shared environmental influences on phenotype of interest, and E refers to latent non-shared environmental influences on phenotype of interest; a, c and e represent the portion of observed variance accounted for by A, C, and E, respectively; rc is the shared environmental correlation within twin pairs and is fixed at 1.0 regardless of zygosity; rg = the genetic correlation within twin pairs and is set to 1.0 for MZ pairs and 0.5 for DZ pairs; s represents the sibling interaction effect.