Ōtepoti – A new US study offers precise linking psychological stress to greying hair in people.

Research by Columbia University Vagelos College of Physicians and Surgeons is the first to offer quantitative evidence linking stress to greying hair.

And while it may seem intuitive that stress can accelerate greying, the researchers were surprised to discover that hair colour can be restored when stress is eliminated, a finding that contrasts with a recent study in mice that suggested that stressed-induced grey hairs are permanent.

The study, published June 22 in eLife, has broader significance than confirming age-old speculation about the effects of stress on hair colour.

When hairs are still under the skin as follicles, they are subject to the influence of stress hormones and other things happening in the mind and body.

Once hairs grow out of the scalp, they harden and permanently crystalise these exposures into a stable form.

Though people have long believed that psychological stress can accelerate grey hair, scientists have debated the connection due to the lack of sensitive methods that can precisely correlate times of stress with hair pigmentation at a single-follicle level.

The Columbia researchers analysed individual hairs from 14 volunteers. The results were compared with each volunteer’s stress diary, in which individuals were asked to review their calendars and rate each week’s level of stress.

The investigators immediately noticed that some grey hairs naturally regain their original colour, which had never been quantitatively documented before.

To better understand how stress causes grey hair, the researchers also measured levels of thousands of proteins in the hairs and how protein levels changed over the length of each hair.

Changes in 300 proteins occurred when hair colour changed, and the researchers developed a mathematical model that suggests stress-induced changes may explain how stress turns hair grey.

In middle age, when the hair is near that threshold because of biological age and other factors, stress will push it over the threshold, and it transitions to grey.