You doctor was right, asthma is a chronic diease, once you learn y ou have it, you probably had it all your life, it just wasn't triggerd. Unless you were involved in an accident, and got a lot of polution or smoke or something. I have asthma, and I didn't know I had it until I was in my 30's .
So I guess PTSD could be like this. I just got it a year ago, but felt much better in about 4 months of therapy and EMDR.