Well, according to Psychology Today, it won’t happen over night. But in time, it could lead to some premature graying.

Tyler Cymet is a researcher at Sinai Hospital of Baltimore. And he says consistent mental and physical stress, over the course of many years, can cause premature aging of the whole body – and that includes your hair. Here’s why:

Hair turns gray when the cells that produce pigment stop doing their job. Now, stress doesn’t directly cause these cells to stop working, but it does affect how quickly the hair is shed. And the faster hair falls out and regrows, the more quickly the pigment cells beak down.

Cymet thinks that on average, people today are going gray about 5 years earlier than they did in the 1970’s. He attributes this to a faster lifestyle, poor diet and a lack of sleep – all of which put huge amounts of stress on the body.

Still, although stress is a factor, most scientists believe that going prematurely gray has more to do with genetics. Take CNN’s Anderson Cooper, who started going gray at 20 and was completely gray by age 35. Or American Idol’s Taylor Hicks, whose gray locks first started popping up when he was 15. In extreme cases like these, it’s all about genetics.

So what’s the bottom line? For the most part, your genes determine when you’ll go gray. But stress is also a minor player. So slow down, eat right and get plenty of rest. It won’t keep you from EVER going gray, but it can help slow down the process by a few years.