For example, everyone’s disks degenerate with old age. They squash, bulge, even herniate. But only some people experience notable pain from this. And back pain

For example, everyone’s disks degenerate with old age. They squash, bulge, even herniate. But only some people experience notable pain from this. And back pain has been a growing epidemic for decades! Are there physiological differences between people that explain this? Probably. But I suspect in many cases Sarno is right, it’s not purely physical. Look into neuromatrix theory and non-proprioceptive pain for a somewhat more scientific attempt at an explanation.