London - Finding your first grey hair can be a traumatic experience for those of us approaching middle age.
But fear not, because white hairs can apparently grow back to their original colour again – and simply relaxing by going on holiday or, in extreme cases, by getting a much longed for divorce could make it happen.
Just as many have long suspected, a study has discovered that stress may cause human hair to turn grey.
More hopefully, however, the researchers found an end to that stress may cause hair to grow back in its old colour.
The study recruited 14 people, aged up to 65, who said they had grey or "two-coloured hairs", with scientists plucking out these offending hairs to analyse them more closely.
They found grey hairs growing dark again at the roots and also discovered that grey hairs could appear and disappear within three months on average and within 3.7 days at the fastest rate.
Measuring the grey to see when it first appeared, researchers could compare this against a "stress graph" drawn for the previous 12 months.
Participants were asked to select the most and least stressful events and mark them on a timeline. The two most striking examples included a 30-year-old woman whose hair turned grey over two months when her marriage was ending, before going back to normal once it was over.
A 35-year-old man saw his grey hair become dark again during what he described as the least stressful month of the past year, when he was on holiday for two weeks.
The authors, including a team from Columbia University in the US, conclude: "We identify white hairs that naturally regain pigmentation within days to weeks in healthy young individuals across sex, ethnicities, ages and body regions, demonstrating that human hair greying is naturally reversible."
David Fisher, professor of dermatology at Harvard University, who was not involved in the study, said: "I believe that most hair greying that bothers people is progressive and rarely reversible. It is clearly associated with ageing and may well include a component of stress, which may be linked to ageing and may accrue with time. However, it does appear some strands can turn back from grey to a more usual colour and it will be interesting to understand if the mechanisms which make this happen could be used to develop a drug which might prevent people going grey more generally. More research is needed to look at this."
The study, reported in New Scientist magazine, has not been published in a scientific journal or been peer-reviewed.