All of them quickly turned gray during their presidency. Why? One word - stress.
As the stress triggers this condition, it causes the hair to fall out and every time a follicle loses a hair, and the hair grows back, it uses up pigment.
So, when each new hair follicle is replaced, pigment is used. Once the pigment runs out, gray or white hairs appear.
Now, as President Obama enters his second term, it's hard not to notice the fast-spreading speckles of white in his dark hair. And with the economy, gun control and overseas conflicts on his plate, he may see more speckles to come.