Stress does turn hair gray but it might be reversible, scientists say

If you’ve noticed you’re losing your natural hair colour, you can make the grey go away by living a less stress-filled life, a new study shows.

Scientists in New York found that when people with grey hairs avoided stress, new hair growth was closer to their natural colour. 

The team took hairs from the heads of volunteers and created an imaging method that detects pigment throughout a hair, from base to tip.  

Stress-induced changes in the mitochondria – the ‘powerhouse’ of each human cell – causes changes to hundreds of proteins in the hair, causing greying, they say.  

The study has been led by experts at the Columbia University Irving Medical Center in Manhattan, New York, who claim to have provided the first quantitative evidence linking psychological stress to greying hair in humans.

‘Understanding the mechanisms that allow “old” grey hairs to return to their “young” pigmented states could yield new clues about the malleability of human ageing in general and how it is influenced by stress,’ said senior author Professor Martin Picard.

‘Our data add to a growing body of evidence demonstrating that human ageing is not a linear, fixed biological process but may, at least in part, be halted or even temporarily reversed.’

The researchers noted that reducing stress won’t necessarily turn your hair to a normal colour if you’re very young or very old. 

‘We don’t think that reducing stress in a 70-year-old who’s been grey for years will darken their hair or increasing stress in a 10-year-old will be enough to tip their hair over the grey threshold,’ said Professor Picard.       

Hair starts growing at the bottom of a hair follicle – the tunnel-shaped structure in the epidermis, the outer layer of the skin.

When we are young, our hair is coloured by the pigments produced by cells in the hair follicle known as melanocytes.

As we grow older, the melanocytes gradually become less active, so less pigment is produced, the colour fades, and grey hair grows instead.

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

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

Hair that has already grown out of the follicle does not change colour, however. 

For their study, the researchers analysed individual hairs from 14 volunteers – seven females and seven males – with an average age of 35. 

The team captured highly detailed images of tiny ‘slices’ of human hairs to quantify the extent of pigment loss (greying) in each of those slices. 

Each slice, measuring about one 20th of a millimetre in width, represents about an hour of hair growth. 

‘Just as the rings in a tree trunk hold information about past decades in the life of a tree, our hair contains information about our biological history,’ said Professor Picard.  

‘If you use your eyes to look at a hair, it will seem like it’s the same colour throughout unless there is a major transition. 

‘Under a high-resolution scanner, you see small, subtle variations in colour, and that’s what we’re measuring.’ 

The results were compared with the contents of a stress diary completed by each volunteer. The individuals were asked to review their calendars and rate each week’s level of stress in the diary. 

When hairs were aligned with stress diaries, striking associations between stress and hair greying were revealed.

Hair colour can be restored when stress is eliminated from our lives, reveal experts at Columbia University Irving Medical Center in New York (stock image)

Some grey hairs were shown to naturally regain their original colour with the lifting of stress, the team found.  

‘There was one individual who went on vacation, and five hairs on that person’s head reverted back to dark during the vacation, synchronised in time,’ Professor Picard said. 

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 in mitochondria may explain how stress turns hair grey. 

‘We often hear that the mitochondria are the powerhouses of the cell, but that’s not the only role they play,’ Professor Picard said. 

Hair pigmentation patterns of 100 hairs from a male and female study participant. Darker hair colors represented in red; lighter in blue

‘Mitochondria are actually like little antennas inside the cell that respond to a number of different signals, including psychological stress.’ 

Last year, a study in mice found that stress-induced greying was caused by an irreversible loss of stem cells in the hair follicle.

But authors of this new study, published in eLife, believe the impact of mitochondria is a more accurate explanation. 

‘Our data show that greying is reversible in people, which implicates a different mechanism,’ said co-author Ralf Paus, a professor of dermatology at the University of Miami. 

‘Mice have very different hair follicle biology, and this may be an instance where findings in mice don’t translate well to people.’