Yes, there’s some physical mechanism, but triggered by emotional responses.

Speaking for myself, I don’t have serious back pain, but when I occasionally experience momentary strong anxiety my back muscles get noticeably tight/strained, especially while sleep deprived. Drinking 1 beer typically alleviates that, or I’m sure some other anxiolytic medicine could.

I would not be surprised at all if chronic severe anxiety (e.g. taking care of a chronically ill child, working a high-stakes short-deadlines job, living with an emotionally abusive person, experiencing trauma and then suffering PTSD, ...) might cause me to develop a real back pain problem.