A new study has produced first-of-a-kind scientific evidence of this connection, identifying proteins in human hairs that seem to drive this process, while also demonstrating how it might even be reversed.The study was carried out by scientists at Columbia University who took aim at what they see as a gap in this type of research so far. While psychological stress has long been seen as a driver of graying hair, it has been difficult for scientists to connect the dots, as correlating hair pigmentation with times of individual stress is a tricky undertaking.