Hello NoBull: I see this is your first post here on PC. So... welcome to Psych Central. The Self-Injury forum, here on PC, may also be of interest to you. Here's a link:

https://psychcentralforums.com/self-injury/

I can't give you an authoritative answer with regard to your question. What I can tell you is that, a number of years ago, I self-harmed until I did permanent damage to myself. After that I stopped. But I still feel the urge to do it again. And if it weren't for the fact that I could, potentially, cause myself even greater permanent injury, I would do it again.

I suppose there's some neuroscientific explanation for what causes one to want to self-harm... something involving neurotransmitters & the release of endorphins perhaps? But I'm not a neuropsychologist. So I can't really speak to that. I only know, from personal experience, that there is something addictive to self-harm. Perhaps other PC members will have other thoughts on the subject.

Here are links to 2 articles, from Psych Central's archives, that speak to the question of what causes people to self-harm:

Self-Harm | Addiction and Mental Health Demystified

The Psychology of Cutting: The reasoning behind self-mutilation

I hope you find PC to be of benefit.