Hi Lucia,
back pain is usually due to a weakening and imbalance of the structure, so it can appear in chronic stress phases (like when through weakening a disc ruptures and pressure gets to the nerves going out from the spinal chord) and especially in the oedematous beginning of regeneration. Especially then this pain can be aggravated by KCT (so this is an overlap of one regeneration phase after self-devaluation plus one stress phase of abandonment) but they don't necessarily go together.
Ankylosing Spondylitis is a chronic on-off pattern of deep self-devaluation, someone who constantly proves himself and yet never "is enough". Naturally, this condition is started at the imprinting stage in childhood, or is even inherited. Question is if these persons tend to isolate themselves because of this belief, thereby self-triggering KCT.
Your friend who worried about survival seems to have had brain stem conflicts, but with chronic self-devaluation it's a dangerous combo, and suicidal means there was even a cortex constellation about losing his position and not feeling loved...
We'll come to the cerebral cortex soon.