I am not sure about the "chronic pain", but I have seen many benefits from a chiropractor.
I, initially, went because my back was out. It hurt to breath, stand, walk, open my eyes (ok maybe not that lol). It took a few weeks to adjust me back, but it was worth it.
Our bodies go through a lot & I have returned periodically to him over the years for adjustments here & there.
I can tell you that my pfts went up dramatically after my initial adjustment. Sadly tho that was the only time they improved from the chiropractic care. I also had "gallbladder" type issues that were corrected from the care.
I have a friend with terrible asthma & sinus issues that goes occaisionally & being adjusted works. Now I use to laugh at her going, but then I got thinking....
When I have a head cold & my nose is stuffed up. Often times I can move my head to a certain position & it opens up the airways so there is something to the whole idea.
Many people shy away from them & I will say that you need to be careful because not all Chiropractors are good & will keep you coming back. That gives the whole practice a bad reputation.
Another thing that is great for pain management (tho I havent personally tried it just know TONS of people who have) is accupuncture. It uses the trigger/pressure points of the body that are connected to different areas.
Good Luck~~