I am working on a study in which we test the effect of a behavioral variable X on a difference score variable Y. The difference score is build out of two distinct factors (Ya - Yb). However I know scholars such as Edwards strongly recommend to not just compute in SPSS the dependent variable as Ya-Yb. I found several alternatives for using difference scores such as polynomial regression. But from my understanding, techniques such as polynomial regression can only be used when the difference score is your independent variable.

Besides testing the effect of X on Ya and Yb separatly, I was wondering whether anyone has other suggestions to address the difference score? (which can be performed in SPSS or AMOS)?

Thanks!

Laura