I am working on a study where patients with a chronic disease received a treatment. The goal is to determine the effect of the treatment on various outcome variables. I have pre and post data (before and after the treatment) for the sick patients and also for a control group of patients who are healthy. It would have been considered unethical to withhold treatment from sick patients, hence there was no control group of sick patients who did not receive the treatment.
I plan to analyze the data using linear mixed effects models. I’ve seen examples of how to analyze this type of data when you have pre/post data with a control group, for example including variables in the model such as the time point, whether the individual is in the treatment or control group, and the interaction between the two. However, I’m wondering about the appropriateness of this approach when the control group is healthy patients. Does it really make sense to make comparisons to a healthy group in this way when the goal of the study is to determine what effect the treatment had? By making comparisons to a group of healthy patients, is this answering a different question?
Appreciate any comments. thank you!