Dr. Hibberd's answer:
 

Yes. Age and genetics are the common denominators here. But stress can also prematurely grey our hair, and a mechanism to reverse it has so far eluded us.
 

The lack if pigment in our hair has as much to do with genetics as it does with environmental and lifestyle triggers. Greying seen after chemotherapy will often resolve with time, but sometimes the color returns with a different hue and sometimes not at all.
 

Unfortunately, no definitive anti-grey formula has been found that will work in all people — short of artificial coloring of our hair. There have been many studies reporting improvement of greying with patented hair products, but so far no oral or topical products have been able to hold up under clinical studies that would allow the Food and Drug Administration to approve treatments for premature grey hair.
 

I hope this reality changes in the near future. I would love to see medical science discover a corrective treatment (not a cover up) for greying hair.