While greying is caused predominantly by your genes, some studies suggest that stress may play a part in prematurely turning hair grey. A bad day at the office won’t make a difference. Ongoing extreme stress could potentially turn hair grey earlier, but there are no definitive scientific studies to confirm this. This is thought to happen because your sympathetic nervous system is activated during stress. This can permanently damage the melanocyte cells that are responsible for colouring your hair. As we know, when these cells are gone, you’re left with hair that contains no pigment, so it appears white or grey.