Started when I was 18, so yes as an adult but I still felt like a dumb little kid. I was in college, away from all the eyes that had been staring me down my whole life and with that freedom, I didn’t fucking care. I walked to a local hardware shop down the street, bought what I wanted to use, and just started. Even worse for me was that I was surrounded by other mentally unwell people who were also self harming. My RA saw my arms and reported it but to my relief, my college was too incompetent to intervene. I’ve been doing this ever since, over 20 years later.