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Controlling for covariates in twin(-family-)-models

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twolf's picture
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Joined: 04/24/2020 - 10:51
Controlling for covariates in twin(-family-)-models

Hello,

I sometimes find papers (like for example this one: https://www.psych.uni-goettingen.de/de/biopers/publications_department/pdfs/Kandler_et_al_2016_The_Nature_of_Creativity.pdf) that apply an interesting approach: Within a twin-model, they control for covariates and interpret how this changes the variance components. As far as I know, including covariates is equivalent to residualising the variable of interest as it is often done for age and gender. However so far I was unable to find a detailed justification for this much more extended utilization of this technique, especially using variables that differ between the twins. Is the aforementioned interpretation of changes in the variance components due to adding these control-variables justified? And can this technique also be used in more complex twin-family-models? I guess we would have to assume that the effects of the covariates (and the explained variance) are roughly constant for the parents and the children but is there anything else that I am missing?

Thanks for your help!
Tobias