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诸如严重的情绪悲伤、工作压力等会加速身体的老化？这绝非耸人听闻。美国加利福尼亚大学的ElissaEpel博士领导的这项研究在生物学领域第一次把心理紧张和心理压力与生理年龄如此直接地联系起来。而在上海内分泌领域的专家看来，美国科研小组上个星期轰动世界的这项研究成果非常适合用来解释中国人常说的“一夜白头”。
【英文原文】
Your teenage son wrecks the car. Your daughter shows up with her recently paroled boyfriend.
These are the sorts of things that can make your hair turn gray overnight.
Actually, it's impossible for hair to completely change color overnight. Hair color comes from a pigment called melanin. When hair grows, the cells that form the growing hair accumulate melanin and distribute it throughout the shaft at the center of a strand of hair. The hair's color depends on the number, size, and color of the melanin particles.
Gray hair results when, for some reason, the production of melanin is reduced, or stops completely. When this happens, the hair becomes transparent and all we see are the colorless cells that make up the hair shaft. Although it is common for melanin production to decrease and eventually stop as a person grows older, there is no specific explanation as to why this happens. Heredity seems to play a significant role in determining when the cells that make hair stop making pigment. If you have inherited genes programmed to shut off the production of melanin at an early age, you'll go gray sooner than later.
The phenomenon of suddenly going gray due to stress has more to do with hair loss than with actually losing color. A significant amount of stress can cause hair to fall out prematurely. If you already have a significant amount of gray hair, the remaining dark hairs might be in a non-growing, resting phase, and thus are more likely to fall out. The sudden loss of dark hair will make it seem as though you've gone gray overnight.
