Recently, it was evaluated to see if there was a genetic component to this condition. A new study in Denmark looked at this and found that children who have an older sibling, one who had autism, were seven times more likely than other kids to be diagnosed with the disorder themselves.
Hair cells, divide so often, that they can duplicate themselves in a few short hours. Some divide faster, that is why some hair grows quicker. As we get older, the cell division, for the most part, slows down. Only the cells of bone marrow grow quicker. Pigment changes results in hair color graying.