Close-up of a woman with visible grey hairs, depicting the natural process of hair turning grey with age. Understand the science behind graying hair.
We’ve all seen those striking before-and-after photos, perhaps of presidents or celebrities, where time seems to be etched in silver strands. Looking at images of Barack Obama before his presidential campaigns compared to after leaving office, the shift from predominantly brown to significantly grey hair is undeniable. It’s a common assumption that stress, particularly the high-stakes stress of leading a nation, is the culprit behind this change. But is stress truly the primary driver of grey hair? And more broadly, Why Does Hair Turn Grey as we age, even for those of us whose daily lives are less demanding than running a country?
Contrary to popular belief, stress is not the main reason most of us develop grey hair. In fact, hair doesn’t actually “turn” grey. The color of each hair strand is determined when it’s produced by the hair follicle, and this color remains constant throughout the hair’s life. If a strand emerges brown, black, red, or blonde, it will stay that color unless artificially dyed. The real explanation lies in the gradual reduction of color production within our hair follicles as we get older. As hair naturally sheds and regenerates, the new growth is increasingly likely to be grey, starting typically around the age of 35. Genetics play a significant role in determining when this process begins for each individual.
The Hair Color Mystery: Understanding Melanocytes
To understand why hair turns grey, we need to delve into the biology of hair pigmentation. Hair color is produced by cells called melanocytes, which are located in hair follicles. These melanocytes produce melanin, the pigment responsible for not only hair color, but also skin and eye color. There are two main types of melanin: eumelanin (for brown and black hues) and pheomelanin (for blonde and red shades). The specific ratio and amount of these melanins determine your natural hair color.
As we age, melanocyte activity naturally decreases. This means that the follicles produce less melanin. When a hair follicle produces less pigment, the hair strand that grows will have less color, appearing grey, silver, or white. It’s not a sudden “turning” grey, but rather a gradual fading of color in new hair growth.
Stress: A Contributing Factor, Not the Root Cause
While stress isn’t the direct cause of hair strands changing color, it can indirectly influence the greying process. Stress can trigger a condition called telogen effluvium. Telogen effluvium is a temporary hair loss condition where stress causes hair follicles to enter the resting (telogen) phase of the hair growth cycle prematurely. This leads to increased hair shedding, often about three times faster than normal.
The good news is that telogen effluvium doesn’t cause permanent baldness; hair does grow back. However, if you are middle-aged and experiencing stress-induced telogen effluvium, the hair that regenerates might be grey instead of your original color. This is because the melanocytes are already naturally producing less pigment due to aging, and the newly grown hair reflects this diminished melanin production.
It’s also worth noting a 2020 study conducted on mice that demonstrated a direct link between stress and grey fur in these animals. The study suggested that stress can cause the depletion of melanocyte stem cells in hair follicles. However, it remains unclear to what extent these findings translate to humans and how significantly stress directly contributes to human hair greying. Current understanding suggests that stress is more of an accelerant in individuals already predisposed to grey hair due to age and genetics, rather than the primary cause itself.
Health Conditions Associated with Grey Hair
While most grey hair is a natural part of aging, premature greying, especially before the age of 30, can sometimes be an indicator of underlying health issues. Certain medical conditions have been linked to earlier onset of grey hair, including:
- Vitamin B12 Deficiency: Vitamin B12 is crucial for various bodily functions, including hair health and pigmentation. A deficiency can lead to premature greying.
- Neurofibromatosis (Von Recklinghausen’s disease): This genetic disorder causes tumors to grow on nerves and can affect hair pigmentation.
- Tuberous Sclerosis: Another rare genetic condition causing benign tumors in multiple organs, which can also impact hair color.
- Thyroid Disease: Thyroid disorders, such as hypothyroidism and hyperthyroidism, can disrupt various bodily processes, including melanocyte function and hair pigmentation.
- Vitiligo: This autoimmune condition causes the loss of melanocytes in patches of skin and hair, potentially leading to localized grey or white hair.
- Alopecia Areata: This autoimmune disorder causes patchy hair loss, often preferentially targeting pigmented hairs while leaving grey hairs behind. This can create the illusion of sudden greying, as the remaining grey hairs become more prominent. When hair regrows, it may initially be grey or white, but natural color can sometimes return later.
If you experience significant premature greying, especially accompanied by other symptoms, consulting a healthcare professional is advisable to rule out any underlying health conditions.
Genetics: The Root of Grey Hair
Ultimately, the timing and extent of your hair greying are largely determined by your genes. Your genetic makeup dictates how quickly your melanocytes reduce melanin production and when this process begins. While stress and certain health conditions can play a role, your family history is the strongest predictor of when and how much grey hair you will develop. So, if you’re wondering when you might go grey, looking at your parents and grandparents is a more reliable indicator than worrying about your current stress levels. This holds true whether you’re leading a nation or navigating the everyday stresses of life.
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About the Author
Robert H. Shmerling, MD, Senior Faculty Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing
Dr. Robert H. Shmerling is the former clinical chief of the division of rheumatology at Beth Israel Deaconess Medical Center (BIDMC), and is a current member of the corresponding faculty in medicine at Harvard Medical School. … See Full Bio
View all posts by Robert H. Shmerling, MD
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