as much as I can by my own assumptions. I believe the stimulus you get from an orgasm increases certain chemicals and hormones like serotonin and (this is from Wikipedia) The period after orgasm (known as a refractory period) is often a relaxing experience, attributed to the release of the neurohormones oxytocin and prolactin, as well as endorphins (or "endogenous morphine").[4]

when you are mentally unhealthy you look to things that have that addictive feel good as well. with sex being so natural and fun and feel good, it's an easy thing to get into for a temporary fix. whatever it is that makes you do the risky sexual activities is probably whatever it is that makes you cut or suicidal or act out. but that's just a guess.