Ah, yes, I was thinking "trauma" as in the really severe stuff that messes people up completely. Like, I have one friend who was left on the steps of a church as a baby, and the church gave her to a couple who'd recently lost their own child. Going through life with the weight of being a "replacement" child was definitely traumatizing for her. But defining it as any "deeply distressing or disturbing experience" would definitely be accurate for all adoptees, and it would depend upon their later circumstances and personalities how (or if) that manifests. I was much more traumatized by a hospital stay when I was 4 for an allergic reaction to a bee sting -- that required actual therapy as an adult to deal with. It's funny that you mention genetic mirroring... I actually look virtually identical to a distant (2nd or 3rd) cousin in some pictures. I haven't read either of the books you mention - I never particularly explored research on adoption.