Most gray hairs in humans are not related to stress. The hair does not turn gray because once a hair follicle produces hair, the color is already set, according to Harvard Medical School Health Publishing.

Hair follicles typically produce less color as they age. That means hair will be more likely to grow in gray through its natural cycle of dying and regeneration beginning after the age of 35. Genetics plays a significant part when this begins.

Although psychological stress could not turn the gray hair, it can trigger telogen effluvium, a common condition that causes hair to shed three times faster than normal. It does not cause balding, but middle-aged people could observe more hair falling out and regenerating more quickly due to stress and produces new hair that will be gray instead of its original color.

A new study led by researchers at Columbia University Vagelos College of Physicians and Surgeons offers quantitative evidence linking psychological stress to premature graying of hair in people, Science Daily reported.

Age-Related Process Could Be Associated with Psychological Stress

The study, entitled "Quantitative mapping of human hair greying and reversal in relation to life stress," published in eLife, confirms the age-old speculation of the effects of stress on hair pigmentation.

Martin Picard, Ph.D., study's senior author and associate professor of psychiatry and neurology at Columbia University Vagelos College of Physicians and Surgeons, said that the hair contains information about a person's biological history. They are influenced by stress hormones while they are still under the skin as follicles.

Ayelet Rosenberg, the study's first author and a student in Picard's laboratory, developed a new method to capture highly detailed images of tiny slices of hair to quantify the extent of hair pigment loss.

Picard says that under a high-resolution scanner, small and subtle variations of pigment can be seen that are not typically observable with the naked eye. Researchers analyzed samples from 14 participants and compared them with their stress diary, a calendar that measures their stress levels every week.

They noticed that some gray hairs regain their original pigmentation, which had never been observed before. Shannon Rausser, second author on the paper and a student in Picard's laboratory, said that stress diaries showed associations between psychological stress and hair graying and, in some cases, a reversal of graying when stress is eliminated.

This implies that the aging-related process is closely associated with the psychological well-being of a person. Picard had been studying for many years how cells grow old at various ages. But the findings of this study show that the aging process is visible on the hair, wherein they do not turn gray at the same time.

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Reversing Graying of Hair

Most people start to notice graying of hair during their 30s or late 20s. Scientific American reported that this period probably is when the process is most reversible. But those with a full head of gray hair have presumably reached a point of no return.

The study shows that at the individual hair level, repigmentation of hair back to its original color is possible. Researchers noted that this mechanism might not only apply to hair as it could also be observed in a variety of tissues where biological changes happen as a person ages.

The analysis showed that the graying or repigmentation of hair corresponded to periods of significant stress or relaxation. One participant who went for a two-week vacation underwent repigmentation of his graying hair. While another participant was observed to have one strand that contained a white segment that corresponded to her most stressful period as she underwent marital separation.

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