Mental health is very subjective, as has been mentioned we're all a little bit messed up so who's to say what "normal" is, there would be many people in civvy life that would suggest that being either a punter or an SP already suggests that we have some sort of mental health issues, but we can all rationalise our involvement, and given that there are more people with classical mental health issues that those involved in the industry perhaps they're right (Surveys suggest approximately 8% of the population use prostitutes and as many as 25% suffer from some sort of mental health problems). There is no normal, we're all different and I would think psychological issues are only as prevalent in either side of the sex industry than in any other walk of life. So it's not a special problem for us.
But the question, "does it matter?" particularly coming from a service provider, is a strange one, we are supposed to completely disassociate the physical and the emotional from the transaction, I wouldn't be ringing up an SP the next day to ask if she had a nice time, it's over, no more than I would expect her doing the same, and not just to be discreet, if I was concerning myself too much about the feelings of an SP then I would have a problem, so it's not that that we don't care it's more that we can't.