Great question.
I think it depends on a bunch of factors:
1) What would be your goal in telling them?
2) What kind of relationship (quality-wise) do you have with them now, and how invested are you in a future relationship with them?
3) How do you think they’ll respond?
4) How do you think their most likely response will affect you?
5) Will your relationship change as a result of this revelation, and if so, will it likely be an improvement?
I have had mixed results after having told, at different points in my life, a small, select group of people about what happened to me and (after my diagnosis) my CPTSD. In one case, it majorly backfired because the person I told happened to be angry with me over something at the time and thus had no compassion for the fact that I had a serious mental health issue and instead threw it in my face, claiming that he had once known someone who (according to him) had had it “much worse” than I had, and he therefore basically yelled at me that I should shut up and just be glad it wasn’t worse. Mind you, that person I had told, by his own admission, had never himself been abused... and yet apparently he was an expert on the topic and felt well within his right to judge my sense of suffering and how I had consequently developed as a human....
Luckily that was the only really negative response I’ve ever received. It did happen a long time ago, though, and was one of the first times I had tried reaching out to someone. After that, I was very cautious about revealing my stuff to others.
One positive outcome is that I have told my current partner more than I’ve ever told anyone (except in a therapy context) and he has been very compassionate about it and has shown so much understanding about all my deficits that stem from CPTSD. In many ways, he has helped me get by day-to-day. So, in the end, I’m very glad I decided to open up to my partner.
My main lesson from all this is to be careful whom I tell, and make sure I only tell someone who I know is safe to tell. I guess one other consideration is whether you might be burdening the other person. Depending upon what you want to tell, and how that person is wired, it may be too much for them.
Finally, remember that once the cat’s out of the bag, you’ll never be able to undo it. Also realize that to some people, it may sound like you’re “just making excuses”. No matter how bad the abuse was and how dysfunctional you may feel as a result of it, many people will be dismissive (not everyone, certainly, but just be prepared for that possibility). Personally, I know that having my suffering dismissed offhandedly by others is EXTREMELY triggering to me, so I generally don’t risk the revelation unless I feel strongly compelled and believe that it will be safe
