Firstly, if you are a reader in the UK, apologies as the click through article uses the U.S. spelling of grey (gray).
Now with that major worry and stress out of the way, we can turn to what turns you grey - it may in fact be worry or anxiousness (like a different spelling), but there is far more than just that as we shall see :
1. It may be a medical condition - possibly Ischemic Heart Disease (IHD), thyroid issue, or deficiency of vitamin B-12. Rest assured, this is a rare sign of early greying.
2. Smoking - not only does it affect the lungs, heart and skin, but also the hair follicles.
3. Chronic Stress - it is not just the stress (you know, that pounding pain in the temple, the very place where the first grey hairs emerge) which causes the issue, but all the other knock on issues such as poor diet, lack of rest, pollution etc
4. Vitamin Deficiency - a lack of B-12. Great sources of this can be found in eggs, milk, meat, fish and poultry. Not the best of news for vegans.
5. Hydrogen Peroxide - As we age, the body makes more Hydrogen Peroxide, which can accumulate in the hair follicles. This can be treated though.
6. Genes - If it's in your genes, it's in your genes - so stop worrying about it - because that itself can bring on greyness!
Again, we see that there are many reasons for many things. Nobody knows what has caused what to who, or how it happened. Let's not judge or make stories up about others, you will only create worry, and that may lead to greyness.
The hair follicles below our scalp grow old just as we do. As we age, our hair follicles produce less melanin, which results in our hair turning grey and then ultimately, white.