CBT is great, but different therapists can be quite, well, different. I had one who was just too harsh, I wish I'd tried another but I just figured that's how it was. But if something traumatic did happen, CBT therapy isn't the place to go -- for that you need more talk therapy as well. CBT therapist don't care a whit how you got this way, they just try to reprogram you, but if you have a depressed attitude CBT won't work, you have to be very involved and motivated for it to work. Hope you work this out.
He has gone through therapy. Tried CBT, the doctors insist that something traumatic happened when he was a child but can't figure it out.
You only mention medication. There are a million different forms of therapy, with CBT considered the best but you have to keep searching. There is also natural medicine to try. There's always something else. One would also want to know if he's exhausted all possible physiological causes. Keep in mind that childhood anxiety is generally thought to be a different creature entirely than adult anxiety, but if it's been constant six that young there might be something that happened that set this off. But, sigh, some of us are just not amenable to therapy.