why do people starve/harm themselves?

[Shea]

everywhere i go, whether its school or another public place or even social media, i see young girls and boys struggling with things like depression and cutting and starving themselves. im pretty young too. (13) but i dont understand why people would do that to themselves at such a young age. dont they know their young bodies are still developing? dont they know the "perfect" girls in their thinspo are probably dead by now? and why do people post pictures online of their scars? doesnt wallowing in their sadness make them even more depressed? arent they triggering other people? maybe im just ignorant, but if you could explain the human nature of these people, please do so.