What does depressed morning cortisol mean?

Non-specific changes: Normally, your cortisol fluctuates a lot during the day, but it tends to be higher in the am than the pm. Because of the wide fluctuation, however, one cortisol measurement does not mean much. The am/pm variation tends to go away when people are sick, and also with depression. This is not the cause of the sickness/depression, but a manifestation of it.

That test was normal: It means that your test, which was probably done looking for cushing's disease, or on a rare occasion depression, is normal.