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. Author manuscript; available in PMC: 2017 Oct 1.
Published in final edited form as: Am J Med Genet B Neuropsychiatr Genet. 2015 Dec 30;171(7):958–970. doi: 10.1002/ajmg.b.32412

Figure 2.

Figure 2

Illustrations of Independent Pathway (Panel A) and Common Pathway (Panel B) models (one twin per pair shown only). Sibling contrast paths and pair-sex covariate not shown. In the Common Pathway model, factors Ae and Ee are the common additive genetic and non-shared environmental factors, respectively, whereas factors Ao, Eo, Ac, Ec, Ah, Eh, Ai, and Ei are the specific factors. Paths are estimated but, for ease of reading, are not labeled. Common factor loading for ODP constrained to 1 to identify the externalizing (EXT) factor. CP = conduct problems, H/I = hyperactive/impulsive ADHD symptoms, In = Inattentive ADHD symptoms, ODP = oppositional/defiant problems.