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Shades of Grey. Gotcha. When you clicked, maybe you thought I would be talking about what goes on in a very popular book series. Nope, not even. I am going to talk about whether your kid really can turn your hair gray.

We've heard our mothers say that someone stressed them out so much it turned their hair gray, or that an acute stress turned their hair white overnight. There are some references to it in the "Talmud," the Jewish holy book, and supposedly Marie Antoinette, the last Queen of France, had her hair turned white overnight between the time that she was sentenced to the guillotine to the next morning when she met with the guillotine. Of course, that's very unlikely, and maybe being a queen during the French Revolution was so stressful that her hair turned white over several months and she covered it with a wig. And when she took it off at her final performance, her hair was white.

First, a little discussion on the anatomy of the hair follicle. The hair is produced under the skin in a hair follicle that's lined with pigment-making cells called melanocytes. Melano means dark or dark-colored and cytes means cells. Melanocytes are in our skin and make pigment either naturally, given our genetics, or when we tan. For those of us who are freckled, we have patches of melanocytes that make more pigment.

In the hair follicle, the melanocytes arise from stem cells that replenish the number of melanocytes. As these stem cells divide, some become melanocytes and some stay as stem cells. This is a strategy for cells that are renewed all over our body. As we age, we run out of stem cells, so we don't make so many new specialized cells like melanocytes. That means no more color to the hair as we age. At least that's the theory. Genes and diseases, like autoimmune diseases, can determine when and if you go gray.

So back to the stress theory. Some clever researchers at the Harvard Stem Cell Institute just reported some interesting studies in mice in the journal "Nature." So, first, they thought maybe going gray was the loss of the melanocytes from an immune problem. It's known that some people with immune problems go gray. So they injected mice with capsaicin, the stuff in chili peppers, which is known to cause an immune stress response in mice. They did this in mice without immune cells, and the mice went gray. So it wasn't the immune system in this case.

The second was to stress out the mice in another way. They were exposed to short-term pain or stressful living conditions in their cages, and they went gray. But was this due to cortisol, which our adrenal gland and mice's adrenal glands make when they get stressed out? Or was it something else? So they took out the adrenal gland of the mice, and they still went gray. By the way, the human race owes the mouse race a serious debt of gratitude for all that they go through for medical research.

So maybe it was the sympathetic nervous system. Each hair follicle has nerves around it. Your hair stands up when you're scared. And when the mice were stressed acutely, their nerves were flooded with norepinephrine. When that happened, all the melanocyte stem cells got programmed to make melanocytes. So there were no more stem cells left to make melanocytes in the future. Now, this didn't happen overnight, but a relatively short period of time. And then the mice didn't have any more stem cells. They didn't have any more melanocytes, and they went gray. So this is a plausible reason for the old wives' tale that acute or chronic stress can turn you gray.

So what do you do about this? Well, having gray hair is a sign of wisdom. You let the gray hairs figure it out. Maybe people who've been through a lot of stress and survived it have a visible cultural signal of their resilience -- their gray hair. Of course, we could suggest that you avoid all stress, but that's pretty hard to do and impossible if you have any kids or any kind of extended network of people you love.

So you can love your gray. For American women over 50, we don't do that so much. It's been suggested that at some time 90% of women over 50 dye their hair. When you finally decide to go gray, you can dye your hair white, but that would be a shock. You could color your hair but put gray highlights and then let it grow out. You could color your hair gray with colored highlights and let it grow out. Best of all, you shouldn't even listen to me because I'm clueless. Talk to your colorist about what's the best way to go gray gracefully, but don't stress out about it.