Let me try one more time.
So you have two models. For the first model,
Outcome/response variable (y): mental health symptoms (behavioral variable)
Predictor (x): baseline fMRI effects at a list of ROIs
For the second model:
Outcome/response variable (y): mental health symptoms (behavioral variable)
First predictor (x1): baseline fMRI effects at a list of ROIs
Second predictor (x2): stressful events (behavioral variable)
Is this accurate? If so, you can follow Example 3 for the interaction between the two predictors.
Make sure that you properly center the two predictors before creating the interaction predictor (the product of the two predictors).
Gang
