I knew when I was in my early 20's but was DX'ed approx. 26 and "didn't like the sound of it", therefore I ignored it until it reared its head so heavy and hard that ignorance was no longer an effective coping tool. I now accept it and am ok with it completely. I knew deep down, before the term BP ever got dropped though. In fact, I was known amongst my friends for being moody. not the BPD type of moody though...they identified mood waves and knew when to stay away from me. three of those friends are still friends to this day and i am grateful. I would say they were the first people to really DX me : )