Ignoring the spiritual part, emotional state does have a well-known feedback loop with physical state. There’s a (largely incorrect) idea in pop psychology that just as happiness leads to smiling, smiling leads to happiness. It’s not nearly that simple, but there are some more straightforward examples: lots of tense emotional states (anger, anxiety) lead to tense muscles (jaw being the classic example). Relaxing your jaw can lead to a (temporary) relaxation of your emotional tenseness. I’ve never heard of a similar result for the lower back, but it’s not hard to imagine. If nothing else, they must be correlated through sedentary lifestyle.
> (largely incorrect) ... just as happiness leads to smiling, smiling leads to happiness.
I don't have a citation to hand and it's really old but there was academic research supporting that at some point. IIRC they used some clever request to get people to move their facial muscles in various ways without tipping them off about what was really going on and then asked them lots of questions that touch on emotional state.
By directing your attention towards, or away from, physical phenomena that mechanically affect your lower back: overexertion, underexertion, posture, nutrient intake, crowd...
Setting the woo aside, there is a lot of data on disorders like central sensitization syndrome that show our psychological state has a very strong modulating effect on our perception of pain.
I mean tons of back pain is medically unexplained. It's not like physiology has a perfect record here that can be used to dismiss alternative theories.
There's a really neat book called Gift of the Raven about an athlete with chronic knee pain that doctors couldn't figure out any plan to stop. He rowed from Alaska to Siberia and the book goes on about a shaman that performs a healing ritual (psychedelic mushrooms were involved) and he finds himself cured. So, there are times I suppose when the pain is all in your head, and maybe has a feedback loop since pain will also cause muscle contraction which can pull bones out of alignment. Relax enough and the pain stops.