I had an interesting experience some years ago. I developed low level pain on my right shoulder blade. Basically it was a slight misalignment of my rib head. The odd thing about it was that it never got bad enough that it reached my full level of consciousness. It did very slowly worsen over time. I remember getting depressed about it. And yet somehow it never really registered as a pain that I should get adjusted.
This went on for about two months. As I recall, the pain worsened to the point where one day at clinic I was doing paperwork toward the end of the day and I made a slight movement which resulted in a sharp jab. That was enough to finally enter my consciousness. I asked the other chiropractor I work with to adjust the rib. That one adjustment was enough to pretty much relieve the pain. Immediately, I noticed a change in my mood and attitude. I could not believe I had let it go that long and how much it had affected me emotionally.
Neurologically, it has been discovered the nerves that transmit chronic pain do synapse with the depression centers of the brain. So quite literally, chronic pain can cause depression.
These days I make it a point to get adjusted regularly no matter what. And I advise my patients to do the same. If a relatively minor pain such as I described can escape my notice and yet still affect me extent that it did, I can only imagine something similar could happen to my patients that are not as attuned to the world of chiropractic.