Testing different types of genotype-environment correlation: an extended children-of-twins model - PubMed (original) (raw)

Testing different types of genotype-environment correlation: an extended children-of-twins model

Jurgita Narusyte et al. Dev Psychol. 2008 Nov.

Abstract

This study presents an extended children-of-twins model, which allowed the authors to test the direction of the association between parenting and child adjustment. Three mechanisms were examined: direct phenotypic influence of parenting on child behavior (controlling for both parental and child genotype), passive genotype-environment correlation, and evocative genotype-environment correlation. This model was tested with Monte Carlo simulations. The authors generated data sets consisting of 1,000 twin parent pairs together with their children and 1,000 twin children pairs together with their parents. These simulated data sets were then used to estimate the model, and the procedure was repeated 1,000 times. The simulation results showed that this model recovered the true values of parameters with high precision. The model was also applied to an observed data set to analyze, as a first example, the association between maternal emotional overinvolvement and child internalizing problems. The results showed that this association was best explained by evocative genotype-environment correlation.

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Figures

Figure 1

Figure 1

Extended children-of-twins model. The model is described in two parts: for twin parents and for twin children. Phenotypes Parenting and Child Adjustment are denoted in rectangles. Genetic (A) and environmental (C, E) influences are depicted in circles. Parenting phenotype is influenced by genetic (A1), shared (C1), and non-shared environment (E1), while Child Adjustment is influenced by genetic (A1′ and A2), shared (C2), and non-shared environmental effects (E2). Measurement error (ε1 and ε2) contributes directly to the variance of both phenotypes. In twin parents part, the genetic effects correlate by 1.0 or 0.5, depending on the twin zygosity. Shared environment (C1) correlated perfectly for both MZ and DZ twins. Genetic effects for children, or cousins, correlate by 0.25 or 0.125, depending on the zygosity of the parents. Shared environmental effects are uncorrelated since the cousins do not share the family. In twin children part, genetic and shared environmental effects correlated perfectly for Parenting phenotype, because there was always the same parent rating both twins. For children, genetic effects correlated by 1.0 or 0.5 for MZ and DZ twins, respectively, and shared environmental effects correlated perfectly for both zygosity groups. Paths m and n denote reciprocity in the relationship between the phenotypes. Path m reflects direct environmental effect of Parenting on Child Adjustment, while path n denotes evocative processes in the relationship. Significant paths m, _a1_′ and a1 will indicate passive rGE, while evocative rGE will be suggested by significant n, _a1_′ and/or a2.

Figure 2

Figure 2

Figure 2a. Results of simulations: the phenotypes were influenced equally by genetics and environment. The dashed line indicates the true parameter value and the solid line denotes the mean of all parameter estimates. Every row of pictures represents the simulation with different values of m and n paths, reflecting different scenarios of rGE presence. Figure 2b. Results of simulations: genetic predominant variance structure of the phenotypes. Figure 2c. Environment predominant variance structure of the phenotypes.

Figure 2

Figure 2

Figure 2a. Results of simulations: the phenotypes were influenced equally by genetics and environment. The dashed line indicates the true parameter value and the solid line denotes the mean of all parameter estimates. Every row of pictures represents the simulation with different values of m and n paths, reflecting different scenarios of rGE presence. Figure 2b. Results of simulations: genetic predominant variance structure of the phenotypes. Figure 2c. Environment predominant variance structure of the phenotypes.

Figure 2

Figure 2

Figure 2a. Results of simulations: the phenotypes were influenced equally by genetics and environment. The dashed line indicates the true parameter value and the solid line denotes the mean of all parameter estimates. Every row of pictures represents the simulation with different values of m and n paths, reflecting different scenarios of rGE presence. Figure 2b. Results of simulations: genetic predominant variance structure of the phenotypes. Figure 2c. Environment predominant variance structure of the phenotypes.

Figure 3

Figure 3

Estimated children-of-twins model for maternal emotional overinvolvement and child internalizing problems. Note. * p < 0.05.

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