It just means at the time of the test you were not experiencing any depression at a level in which it would have showed up on the machine.

At the mooment I can't remember if you have DID or not. those that have DIS have a higher ability to consciously and unconsciously use relaxation skills to the point where they register the equivelent alpha or beta waves that a person under hypnosis, no depression and or being asleep would register. so Im not surprised that the test turned out this way.

Instead of depending on the visual aid of the machines you might have to do your process the same way I do - by paying attention to your heart rate and breathing rate and muscle relaxation instead of brain wave activity.