Feelings are real even if they can not be displayed on a computer screen. It sounds like the test was to look at physiological issues not feelings. If there were a test for depression, I think they would give us that test rather than try to diagnose us by asking us questions. I would love to be able to have a picture that says whether or not I am or have ever been depressed. But, it isn't going to happen. My psychiatrist wants me on an anti-depressant based on nothing but my discussion of symptoms. That is how depression is diagnosed not by some brain waves test.
I'd look into the research on this particular test and on biofeedback. Medline might be a good place to look.