Hello,
some days ago I read the paper by Shaun Purcell (2002) "Variance Components Models for Gene-Environment Interaction in Twin Analysis" and I'm especially interested in modelling a three-way interaction (GxExE). So, for example, the genetic effect may be moderated by the socioeconomic status and by age, so that the additive genetic variance component is:
$$
(a+\beta_{Age}M_{Age}+\beta_{SES}M_{SES}+\beta_{AgexSES}M_{Age}M_{SES})^{2}
$$
Since my goal is to model such a three-way interaction, my question is what software I could use to do so. Since Purcell used for his analysis the Mx-Software, it should be possible to model such a three-way interaction with the R package "OpenMx". My question is: Could I use the "umx"-package as well to model a GxExE interaction? In the "umx"-manual, I have read that it is possible to model a two-way interaction, but I am not sure, if it could be extended to model a three-way interaction.