S&M: Healthy by Definition?

The Sadist by Cambiodefractal on Flickr (http://flic.kr/p/61g6nw)

There is a thread going on in Fetlife about whether or not S&M is actually healthier than vanilla relationships. The initiator of this thread points to the "Hormonal Changes and Couple Bonding in Consensual Sadomasochistic Activity" studies performed in 2006 or so by Sagarin, et al. on 58 S&M couples. The results of which were subsequently published and I've attached them here as well as quoting the abstract:

In two studies, 58...