According to the Mayo Clinic's site, "having been abused or neglected as a child", is one of the risk factors: http://www.mayoclinic.com/health/pos...N=risk-factors

Just long-time neglect could cause present interpretations of neglect by you to "trigger" you. My mother died when I was 3, was sick all my life up until then and not able to adequately care for me and I was badly triggered when I was in my late 40's and my stepmother became senile. Her inability to care for herself reawakened all the terror of "who's going to take care of me?" that I had as a 3 and 4 year old in a household with my working father and three older brothers (in school). I had to help care for my stepmother when I was feeling like a 3 year old myself.

When the maid could not come (she was my primary daily care-taker) and my father had to scramble to find someone to leave me with, often they were a "stranger" to me and not knowing where I was, with whom, if/when my father would return (having already had my mother "leave" me) made me, to this day, feel anxious when I'm in someone else's house; I even have trouble caring for my grandchildren in "their" house. I was lousy at babysitting as a teen, hated it because it made me so anxious but I didn't know why.

I had been out of therapy for nearly 10 years, was happily married to a great husband but had to start therapy again to deal with the anxiety of my stepmother's decline and death (the hospital she was in when ill where I had to visit was the same my mother died in 40+ years earlier).

So, "the" event doesn't have to be anything big, like "war" or a car accident, it just has to be something that forms enough of a pattern in itself so that when the pattern is "repeated" now in some way, it causes you distress.