Yeah, that's been going in and out of style for thousands of years. Sometimes whole countries and religions practiced self injury, some with self denial, some with self flagellation, some with mortification of the flesh. We are pretty tripped out as a species. The psychological release you refer to is probably the justification for the religious aspects. It could be seen as a sign of approval from God if the mind were bent that way already.
I don't know when modern cutters started being popular, or if the numbers are the same and we only notice because of the information age, and the current availability of studies. I suspect that when self immolation isn't in vogue, that as an uneducated group, these people gravitate towards activities that hurt them physically, like carpentry, boxing, bondage sex, football and the like.