Does stress make hair go grey and is colour reversal possible?
Researchers at Columbia University have found ( eLife ) that stress can accelerate greying, and surprisingly the hair colour can be restored when stress is eliminated. They also found that stress does not affect the colour of hair that has already grown out of the follicle. When hairs are still under the skin as follicles, they are subject to the influence of stress hormones. Once hairs grow out of the scalp, they harden and permanently crystallise and serve as record of past stresses, much like the tree rings hold information about past.
The researchers developed a new method to capture highly detailed images of tiny slices of human hairs to quantify the extent of pigment loss (greying) in each of those slices. Each slice, about 1/20 of a millimetre wide, represents about an hour of hair growth.
While the colour difference may not be perceptible to the naked eyes, under a high-resolution scanner, subtle variations in colour were seen. The researchers analysed individual hairs from 14 volunteers. The results were compared with each stress level volunteer on a weekly basis. They found that some grey hairs naturally regained their original colour and when the change in colour was compared with stress levels, a striking association was seen.
Based on modelling, scientists think in middle age, hair needs to reach a threshold before it turns grey. Stress pushes it over the threshold so the hair become grey. While the colour of hair can be reversed when the stress is removed, it cannot be the case in old people.
