Ds1 (4) has just started deliberately scratching himself when he gets angry. If we tell him not to do something or tell him off about something he says he is going to scratch himself and then proceeds to scratch his arm.
At the moment we are just calmly saying "that's not a nice thing to do, don't hurt yourself" and are hoping he will stop when he sees it's not causing much reaction, but I just wondered if others had experienced this and how common it was.