When I was a very young child (say around 2 years old or earlier) I began bumping my head at night to go to sleep. I did this up until I finally broke myself of the habit in my mid-teens. Of course, way back then I wouldn't have even had the capacity to think of it as a "coping strategy". But, looking back, I believe that's what it was. Later in life I returned to hitting my head as a means of self-injury which resulted in me developing Meniere's disease & tinnitus. I don't do it anymore...