An anonymous reader quotes a report from Scientific American: Few harbingers of old age are clearer than the sight of gray hair. As we grow older, black, brown, blonde or red strands lose their youthful hue. Although this may seem like a permanent change, new research reveals that the graying process can be undone -- at least temporarily. In a study published today in eLife, a group of researchers provide the most robust evidence of this phenomenon to date in hair from around a dozen people of various ages, ethnicities and sexes. It also aligns patterns of graying and reversal to periods of stress, which implies that this aging-related process is closely associated with our psychological well-being.
The researchers [...] developed a technique to digitize and quantify the subtle changes in color, which they dubbed hair pigmentation patterns, along each strand. These patterns revealed something surprising: In 10 of [the 14 participants], who were between age nine and 39, some graying hairs regained color. The team also found that this occurred not just on the head but in other bodily regions as well. "When we saw this in pubic hair, we thought, 'Okay, this is real,'" [Martin Picard, a mitochondrial psychobiologist at Columbia University] says. "This happens not just in one person or on the head but across the whole body." He adds that because the reversibility only appeared in some hair follicles, however, it is likely limited to specific periods when changes are still able to occur. Most people start noticing their first gray hairs in their 30s -- although some may find them in their late 20s. This period, when graying has just begun, is probably when the process is most reversible, according to [study co-author Ralf Paus, a dermatologist at the University of Miami]. In those with a full head of gray hair, most of the strands have presumably reached a "point of no return," but the possibility remains that some hair follicles may still be malleable to change, he says.
In a small subset of participants, the researchers pinpointed segments in single hairs where color changes occurred in the pigmentation patterns. Then they calculated the times when the change happened using the known average growth rate of human hair: approximately one centimeter per month. These participants also provided a history of the most stressful events they had experienced over the course of a year. This analysis revealed that the times when graying or reversal occurred corresponded to periods of significant stress or relaxation. In one individual, a 35-year-old man with auburn hair, five strands of hair underwent graying reversal during the same time span, which coincided with a two-week vacation. Another subject, a 30-year-old woman with black hair, had one strand that contained a white segment that corresponded to two months during which she underwent marital separation and relocation -- her highest-stress period in the year.
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