Check this video out. It's long and not DIRECTLY about Our Mysterious Condition - and YET... you will see the connections. The man is talking about the BIOLOGY of depression/stress. SCIENCE!!!
When you get shuffled off to a mental health professional you will very rarely - if at all - hear about the biology of what's going on. Mostly because the folks you are sent to see know very little about it and focus their efforts solely on the behavioral stuff.
You may want to take some notes for further research and maybe listen to it a couple of times.