Have a friend with issues who got back into it when she hit a really rough patch. Whipped out a razor in front of me one day and started going at her arm to "freshen" the scar (she wasn't doing herself much harm, but she was drawing blood, for sure). I really felt like she might be trying to get a reaction, which, fuck that shit; you're a grown-up, use your damn words. And I was doing plenty for her already. Anyway, I just kinda looked at her and dryly asked when the last time we had boundaries was.
Scarification is an even finer line than tattoos between art and NSSI. Which is a whole nother topic or two I could rant about for awhile but won't.
Is that common? It must be hard to have friendships if they make your professional services part of the relationship.
Common for her? She's cooled off it last I checked, or at least she's less flamboyant about it. She was going through a *lot* at the time; I can see how her boundaries and ability to deal with things like a grown-up kind of melted down. But, like I said, I was already doing what I could for her, and having some ridiculous STAHHPPP HURTING YOURSELLFFFF reaction would have done nothing good. My own history with such things (which includes attending training last year, actually- pretty much told me my instinctive responses are about right) has made me not especially freaked out by it, and also aware that making a huge issue of it doesn't help anyone. Honestly, I also kinda feel like what people do to their own bodies ought to be their business. I understand the ethical need to intervene if someone's doing life-threatening damage, but superficial cuts and the like almost feel like nitpicking. (I spend a lot of time trying to help people recovering from things like alcoholism and heroin addiction and repeatedly diving into relationships with domestic violence and things like that, so I might have a skewed perspective on what battles you ought to pick, lol.)
Common in general? I would have to hunt around to find the stat, but non-suicidal self-injury (NSSI) is actually really common, especially in my generation and down, because the media popularized it so damn much (and it's one of those things that tends to be really socially contagious, especially with kids or pre-established self-injurers).
I think something like 1 in 4 college students had done it at least once. I forget how they defined NSSI in various surveys, though- usually, they focus on cutting, bruising, and burning; sometimes also on skin-picking and hair-pulling, though personally I think that's usually a different animal. If you count the more traditionally "masculine" forms of NSSI (like punching inanimate objects- which, believe me, fucks you long-term more than cutting does- I have at least one client who got arthritis from repeatedly fracturing his knuckles; frankly, getting into physical fights sometimes serves the same purpose for people/similar release, couples with an actual desire to get hurt), I honestly think it's probably even more than that.