How can you tell when they're hurt?

Curious Goldie http://curiousgoldie.blogspot.com/ asks the question: "When your kids are little, you can tell when they're hurt - they cry and wail. How can you tell if your teenager is hurt..."
Of course she was referring to physical hurt, but I wondered: what about psychic hurt? I have suffered a fair amount of it, as I suppose ASpies do, along the way. When it happened, did anyone besides me even have a clue? I don't think so. (Thanks a lot dad.) It still happens - idle comments, attempts at humour, asides, helpful (supposedly) hints that come across as criticisms. Am I being paranoid. Or is it that many people are just plain mean-spirited and that's how they bolster their egos?
I don't take those things very well. I mean, I remember them. A long time. Basically forever.
But it brings me back to the first question - how can you tell when you, as a parent, have psychically hurt your child? Dunno. Wish I did. Just hope I didn't do it too often. Scars are not pretty things.