Well lately I have been asked this question and have read many papers from some pretty amazing people in the field of health and spinal surgery. Some say it is in your head and others say the pain comes first and then affects our mind.
Having gone through my own experience with back pain, I would agree that the pain or injury tend to lead to psychological changes in our brain.
However some will say that our mind created an environment that prevented us from moving correctly. Thus leading to injuries.
Who knows, but as Yogi’s we know we are one big beautiful interconnected species !!!!