A new study provides scientific evidence to support the idea that stress can cause a person’s hair to turn gray. A team from America’s Harvard University said the new study is the first to show a clear link between stress and graying hair. The findings were recently published in the journal Nature. Researchers say they discovered a chemical process that can change hair color during times of stress. The process is linked to the body’s “fight-or-flight” reaction that can happen during dangerous situations.