Figure 1.

Path diagram of the extended univariate moderation model representative of one twin only. Adrenarche or Pubertal Status = moderator; A = additive genetic effects; C= shared environmental effects; E= non-shared environmental effects; M₁ and M₂ =moderator in twin 1 and twin 2, respectively; β_M =phenotypic regression coefficient; a, c, and e = paths or intercepts; β_χ, β_γ, and β_Ζ = linear moderators, β_χ², β_γ², and β_Ζ² = quadratic moderators. Although the model is depicted for only one twin, parameters are fit separately for twin 1 and twin 2 and for MZ and DZ twins. Estimates denoted within parentheses (β_MM₂) are included in the extended univariate moderation model to account for co-twin covariance on the moderator (i.e., adrenarcheal or pubertal status groups).