Purging/suppressing memory (beheading video)

I’m curious as to how long it takes, or how soon, I suppose, someone to suppress a traumatic memory/image.

I know I’ve heard of people subjected to horrific crimes or life-threatening accidents (fire and the like) who have blocked the memory if the event from their mind. Sure, they sometimes (so it seems) have flashbacks or the memory pops back up (with a forceful reaction, no doubt). No cites, it’s just sort of one of those background things I’ve heard/read over the years and I’d be happy to attribute it all to TV or Law & Order or something, but I’m certain I’ve heard/seen stories of such things, so work with me here.

What brought this to mind (pun, I suppose, intended) was a thread I was reading about morality where Priceguy says

This, in turn, triggered the memory of seeing the video of the beheading a few short weeks back, and the realization that I’d successfully blocked it from my mind, despite the sincere belief at the time that it was something I would not soon forget.

So, again, do people who forget such traumatic things usually do so quickly, or does it happen over time and one day they have just forgotten? Or, and I guess this goes without saying, but since we’re here: does it depend on the person, the event and the circumstances?

Follow-up for any Dopers that saw the video in question- had you forgotten about it until reading this?

In 1999, I saw a 73-year-old woman get killed instantly right in front of me. I was also the first non-involved (in the car accident) person on the scene. The poor lady was so tiny and pretty, dressed for church (they were heading home), and I knew as soon as I saw her that she was dead. I was traumatized for days afterwards (my co-workers, all social workers, sent me to Crisis Counseling when I showed up for work the next day), and when reminded, I can still see, hear, and feel the sensations of that awful day.

I think that when people still flash back and can’t forget traumatic events after a long period of time, it’s called Post-Traumatic Stress Syndrome, and this is a very debilitating condition. For most of us, not always remembering awful things makes it so that we can survive and function.

Duh, I didn’t answer your question. For this particular person, it took about three to six months before I wasn’t thinking about or “seeing” the accident on a daily basis. Not sure about stats for anyone else, but there’s some anecdotal evidence for you ;).

I visited a shrink soon after a horrible crime happened in my home, and I asked him how I could ever get it out of my mind. He said, “You never will. However, over time, it won’t be the first thing you think of in the morning. Eventually, you’ll go whole days, and then weeks without thinking about it, and it won’t hurt so much when you do.” It’s been twelve years now, and he was right.