Figure - PMC

Skip to main content

An official website of the United States government

Here's how you know

Here's how you know

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

View full-text article in PMC

. 2022 Nov 2;53(1):63–73. doi: 10.1007/s10519-022-10122-x

Search in PMC
Search in PubMed
View in NLM Catalog
Add to search

© The Author(s) 2022

Open AccessThis article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.

PMC Copyright notice

Fig. 1 — Classic DoC model. Path diagram representing a Direction of Causation model for one twin. This is depicting the relationship between two phenotypes, and the causal paths are estimated affording information from the cross-twin cross-trait correlations. Cross-twin covariance between additive genetic effects is 0.5 (not shown) for DZ twins, as DZs are expected to share 50% of the genetic effects. Standard structural equation modeling symbology is used. Circles represent latent variables, whose variances are fixed to unity. Double-headed arrows are covariances or variances, single-headed are the causal regression paths. Squares represent observed variables. A, C and E are the additive, shared and unique environmental effects. This model is not identified with data from MZ and DZ twins. To make it identified one needs to set to zero any two of the five paths ra, rc, re, g₂ and g₁ (Maes et al. 2021)