I'm not sure but as for me i've had it off and on for as long as i can remember...i haven't really seen any patern either......doesn't matter if life is going well or not or if my helth is good or not.....just one morning i just wakeup with it.......and have no idea how long it'll last.......really very screwy...
btw i'm glad to hear you're begining to come out of it......hope you feelinh better last a LONG time.........JohnD