As everyone has said, the ages vary tremendously. You could be 8 or 40. It is just like anything else - a way to cope. People smoke at different ages, try drugs at different ages, and even drink at different ages. Obviously these things generally start in our teens or when we are kids. I would suggest that that is due to the fact that our teen years are some of the hardest to get through, and it also does not take us long to be unhappy with our lives. This is why many kids/teens find other coping methods. I was personally 17 when I began to cut.