Does stress cause grey hair?

Kat Arney put this question to Chris Smith...

Chris - People have looked at this in some detail actually, and there's not really a consistent story here.

There's a reason, a clear reason, why hair goes grey, or white, because the natural colour of hair - it's a protein called keratin. It's the same protein that makes your fingernails and toenails, and the natural colour of that protein is white.

And the reason hair is coloured is, when hair grows out of the hair follicle, which is a little ring of stem cells embedded in your skin that makes the hair, there's another population of cells in the follicle, called melanocytes, and melanocytes, as you probably know - the clue is in the name - make melanin.

There are different "flavours" of melanin, the chemical. There's what we call eumelanin, which is a very black colour, and there's phaeomelanin, which is a more yellow colour; and the different ratio of these (the black to the yellow) affects the colour of the hair. These melanin pigments are added to the hair as it forms, and that gives it it's colour.

For some reason, as we age, the hair follicle soldiers on but the melanocytes peg out and die; they stop making a colour-contribution to the hair and it reverts to its natural state, which is a white colour.

Whether or not this can be the consequence of stress, actually, we just don't know. One way that could happen is because, for instance, the follicles become biochemically stressed. Perhaps when you are under periods of extreme stress it could biochemically stress the hair follicles - but there's not really any good evidence for that.

Another reason, people have speculated - and it's certainly been shown in animals - that there's a build-up of hydrogen peroxide at high levels in hair follicles, and that hydrogen peroxide can damage the melanocytes. So, perhaps, for some reason when you're stressed you have less ability to defend yourself against hydrogen peroxide attack?

On the whole, we're pretty unconvinced and it's probably genetic because some people keep their hair colour for much longer than others and that tends to run in families.

So, it doesn't actually look like Barack Obama's grey hairs are down to increased stress in the job, it's probably just a lack of "Grecian 2000"!