I used to self-harm and I did it for several reasons. I was depressed back then, but I have times outside of depression where I have the urge, so I do believe it could be my AS (or ADHD, if we think about impulsivity)
Some reasons for why I did it would be that I was stressed out because of school, experiencing intense emotions or finding it hard to express them in a better way, or simply I just wanted to have a visible sign that people could see so they'd know that I wasn't okay. Some sort of "fragile, handle with care" warning, almost. I'll have to admit that sometimes I did it for very stupid reasons too.
It felt good and self-mutulation comforted me. It became a coping mechanism. It sort of feels like rain dripping on me. I don't reccomend it though, oddly enough. I haven't properly cut myself in several months now. However, I self-mutulate probably weekly, but it doesn't give me scars at least and I've done it since childhood anyways. Bad habit, I suppose.
hope nobody got inspired to try it themselves now. It's not a healthy way to deal with your problems. I understand it though, I do.