Watch a medical analysist talk about SI while Seventeen magazine editor sits awkwardly to the side.
I don't think Dr. Snyderman's analysis is the primary factor in most cases. Almost everyone who cuts that I've met experiences self-loathing to various degrees, but we consist of more than our bodies. Inside our minds, we hate ourselves for not being good enough; for always being wrong; for being useless; for not being able to cope with stuff beyond our control. Our bodies are the physical holders of our minds, and so we cut them, because it's the easiest outlet to ourselves. Looking like a model on the cover of Seventeen is not, nor ever was, a goal of every SI-ing teenage girl. Some girls may feel the say Dr. Snyderman describes, but cutting can't be obliviated with stickers on all Photoshopped pictures (an idea I completely support) or an outright airbrushing ban.
It bothers me that even with this serious topic all girls are typecasted to shallow, pretty, little things.