Normally, the safe feeling in the chest after a shock will reverse the change in brain chemistry , lowering adrenaline and raising dopamine, but when you are worrying about
the DP, you cannot feel safe.
DP can occur as a result of a trauma. In this case, as well as the above, the brain is taking time out to rest itself ? you have no control over this the more you try , the more tired your brain gets and it can't feel the safe feeling it needs.