I know that in my case, my symptoms were probably triggered by a 15+ hour plane ride, and I was super anxious the whole time. When I got off that plane, I felt very repressed and foggy headed ,much like I am still today. That was in 2009. Before that I was pretty stressed out and drinking a ton of caffeine, which I was already sensitive to. So ya stress/trauma/anxiety probably a factor for most, IMO.