Depersonalizations may occur in cases where the person had been exposed to extreme stress. It is a way of coping.
You've mentioned having used CBT and meds. Other options to treat the anxiety are in the form of hypnotherapy or working with someone specializing/trained in Neurolinguistic Programing.
Self Help tools-
Stop Panic Attacks (Hypnosis) by XXXXX XXXXX
End Anxiety & Panic Attack Self Hypnosis CD ~ Stress Management by Christopher Love (Audio CD)
Guided Meditations for Stress Reduction by Bodhipaksa (Audio CD - Nov 16, 2004)
Why does the response to extreme stress take depersonization rather than another other form of anxiety response. This response makes me anticipate it happening again. Therapy has done nothing to relieve the anticipatory anxiety of this happening again.
People have different coping mechanisms activated during stress. I had suggested hypnotherapy versus CBT (which you had already tried)
The link below is to an on line support group
I did not print out the cds you suggested on hynosis. Could you please send them again.