It's an interesting question. Psychologists studied the monks who came from Tibet and were emprisoned and tortured, and they concluded that they had no PTSD sympthoms. The only explanation is that they practice meditation.
Bhante Yuttadhammo, iirc, told the story of a woman who was abused when she was a child and went to therapists for years and never got over the traumatic event. She was very miserable. He said that she learned to meditate (properly) and she got to a much more peaceful state of mind.
On the other hand, I've read that a person who was abused during childhood, went on a retreat and got out of there earlier and s/he said that it was like living it all over again and that s/he couldn't stop thinking about it.
What lessons can we take from this? In my humble opinion, it's that meditation can help you a lot, but to do it in apropriate dosages.
He turns his mind away from those phenomena, and having done so, inclines his mind to the property of deathlessness: 'This is peace, this is exquisite — the resolution of all fabrications; the relinquishment of all acquisitions; the ending of craving; dispassion; cessation; Unbinding.'
(Jhana Sutta - Thanissaro Bhikkhu translation)