I also do not consider myself damaged and yet I am certainly a sub. I agree that all have some form of mental bruising but the relevance of mental stress is not that it happens but how you deal with it. Things like depression and other serious mental illness can happen because of an individual's response to their environment - some are hardened by adversity, others are destroyed. Of course, neurotransmitters are also involved somewhere but then psychology will never escape the nature/nurture debate

I think a tendency to be drawn to BDSM is more a feature of the variety in mental states. In any variable expressed as a normal distribution there will always be those who are at the extreme ends. This is likely to be independent of any other mental state.