Hi FreeSurfer Experts,

With age as a continuous variable, qdec can test the linear effect of age. To test the quadratic effect of age, do I just create a curvilinear term like age*age and add into the existing equation?

For example:

original equation:  Y = intercept + age + Factor + age*Factor

new equation: Y = intercept + age + Factor + age*Factor + age*age + age*age*Factor

Best,

Daniel