When I was a teenager I used to bite myself when in a situation with a lot of sounds/sights. I have stopped doing that a long time ago, and I do not do that anymore. But, I just remembered it when reading this thread. I think at the time I was doing it to keep from fainting but also distracting myself from the sounds/sights (since I get a lot of sensory overload). Anyway, have not done that for many, many years and when I did it it was just a few times. I know this is not the same as what was asked in the thread, but just wanted to add it because it came back to my memory. Anyway, I do not do self harm otherwise for any other reason, and I also did not do it for attention at the time, even if one of my friends caught me biting my finger and asked what I was doing. So, I told them I was just feeling a bit faint and wanted to make sure not to faint. Dunno if they believed me or not, but they never asked me again after that, and I also made sure to not be around too many sounds and sights in that place again (was a school library with lots of students at certain times of the day, I would go when there were students but less so that you could be in there with people without being overwhelmed).
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Diagnosed Asperger's Syndrome 2017. Proudly Autistic <3