If you have read much trashy 19th Century literature, you will no doubt have run across an example of someone who suffers a terrible shock, and whose hair turns white overnight from the experience. Obviously, this is not possible since the hair on our heads is all dead, but the myth prevails. Annie Oakley is said to have gone white overnight. (Another version of this story has her hair turning white after too much time in a mineral bath at a European spa.) Likewise, Sir Thomas More and Marie Antoinette were reputed to have gone white the night before their executions.
A few years back, I had parts of my head shaved for some minor surgery, so I know exactly the rate at which my hair grows.
Literary conventions aside, I have an astonishing crop of white hairs that exactly coincide with the date of Robb's accident. Stress? You betcha!