Going Grey: Does Stress Cause Your Hair to Lose its Pigment?
Where were you when you found your first grey hair? I was sat in front of my mirror getting ready for another day in the lab when I noticed the silver strand standing out against my red locks. As a 27 year old who is doing a PhD, I thought this hair was a result of one of two things: either the time had struck on my internal clock to start removing pigment from my mane or my highly stressful post-graduate degree was at the root (pardon the pun) of my new silver friend. You may have heard that stress turns your hair grey, but how true is this old wives tale? And if it is true, could this tell us more about how our cells react to stress? New research points to a real biological mechanism linking increased stress to hair pigment loss, hinting those new greys might be a parting gift from that hectic period at work.
Stress Science: What is Stress?
When you are under a lot of pressure in your job or events take a turn in your life, you may enter a state of stress. Physically, a stressful spell can be characterised by an increased heart rate, loss of appetite and sky-rocketing blood pressure. And although we associate feeling stressed with negative connotations, stress evolved to enable humans to fight or flee a tough situation. Stress is activated in the body through signals in the brain. If your brain perceives what it believes to be an incoming threat, the acute stress response is triggered by a brain region called the hypothalamus. The hypothalamus can be regarded as a ‘command centre’ between the brain and the body, and signals to promote the release of noradrenaline from the adrenal glands. Noradrenaline stimulates nerves in the ‘fight or flight’ (aka sympathetic) nervous system, leading to a quickened heartbeat, dilated pupils and increased attention. Stress eventually ceases do to the activation of the slow stress response; switching itself off once the threat has retreated.
There are situations where the stress response is still vital to our survival, like jumping out of the way of a car who skipped a red light or fleeing from a hungry lion (a common event). However, this response was intended to only be used in a life-or-death situation not regular day-to-day events. Too much stress is not good for our bodies or brains and is linked to damaging process such as brain volume loss, increased risk of diseases due to compromised immunity and heart conditions.
I Can’t Divide: Stress and Cell Health
With chronic stress comes severe consequences for the cells of our body. Across different organ systems, you have many different cell types which act in specific ways so your heart beats and your stomach secretes. Some of these cells types are able to duplicate themselves to replace old or dead cells in the tissue in a process we call ‘mitosis’. An example of this process is your skin cells. You shed approximately 40,000 skin cells per minute and these are ‘effortlessly’ (it takes a LAHT of energy for a cell to divide) replaced by the healthy cells copying themselves and fitting into the skin layers. Cell division is impacted by ageing and also by stress, implying tissue systems can be damaged if your stress response is in overdrive for a long period of time. How chronic stress directly impacts cell division is still under investigation and finding a mechanism for this process could aid therapeutic progress for many conditions.
A dividing cell type whose loss is physically obvious are melanocyte stem cells in the hair follicle which mature into melanocytes, aka, the ‘colour-expressing’ cells in your hair. Melanocytes contain the pigment melanin and the type and amount of melanin gives you your distinct hair colour. If you have dark brown hair, this is a result of high levels of eumelanin (brown/black melanin) in your melanocytes, and decreasing levels of this pigment make you more ‘blonde’. For a small percentage of the population (me included!), melanocytes express high levels of red/orange melanin called pheomelanin, and this gives locks a ginger or auburn colour. Irrespective of the melanin in your melanocytes, these cells are replaced by differentiating melanocyte stems cells when one hair falls out and a new one grows through; meaning your new strands are packed with pigment.
Silver Mane: Stress and Greying
As we age, melanocyte stem cells numbers drop. This drop is not due to death of the cells but their permanent differentiation, meaning they can no longer divide to generate replacement cells. The lack of melanocyte stem cells in the hair follicle means new strands do not contain differentiated melanocytes and come through without pigment, leaving them a silvery grey or bright white. The time you grey is down to a mixture of your genes (inherited from your parents) and environmental factors, with stress being a top contender for driving widespread whiteness.
A new study published in January 2020 sort to identify what the biological mechanism could be linking stress to greying. Using mice with dark pigmented fur, researchers induced stress in these animals experimentally and found the mice under stress displayed an increased number of white hairs in their coat. When investigating the mechanism of how stress was prompting this change, they found that activation of the sympathetic nervous system (that ‘fight or flight’ response) was driving the appearance of greys. As we know, the stress response leads to increased release of noradrenaline, and in these mice, these raised levels lead melanocyte stem cells to divide like crazy. This excessive division drove the cells to permanently differentiate and migrate away from the follicle, removing their replenishing source of pigmentation from the hair. This response was inhibited when the noradrenaline receptors – aka the place when noradrenaline binds and induces its actions – where removed from melanocyte stem cells. Although this study was done in mice and really focuses on the acute ‘fight or flight’ stress response, it could be really useful if these mechanisms are also found in people. Not only does this study give us a potential biological basis for how stress could turn hair grey in humans, but also could give us an insight into how stress could affect other tissues in the body in conditions associated with chronic stress.
Stress-related greying is transitioning from a wives tale to scientific hail, with a real biological mechanism coming through for how really stressful situations could induce silvery locks. While we should all embrace ageing and greying as part of life (plus grey hair is so in right now!), the stress-associated loss of hair pigment cells tell us much more about the actual impact stress could be having on our healthy cells. Hopefully this work will further help research into diseases and conditions associated with stress and could provide a really interesting therapeutic avenue. So if you notice a few new white strands after that tough time in work, blame that stress response!
Julia xoxox (@julia.ravey.science)