Re: Can stress really cause (contribute to) whitening of the hair?

Hi Mikael! What a great question! Hair whitening has been extensively 
studied in gerontobiology. I must admit that there is no immediate answer 
to your question but after a quick search in PubMed I think I can provide 
you with some thoughts in this issue.

A short answer to your question is “yes”, stress “can probably contribute” 
to hair whitening in some genetically predisposed individuals. But then 
why? What is the link? First of all we must consider the histophysiology 
of hair follicles. A hair follicle is a sheath of epidermal cells and 
connective tissue that surrounds the root of a hair. The root of the hair, 
beneath the surface of the skin (scalp), is expanded at its base to form 
the bulb, which contains a matrix of dividing cells. As new cells are 
formed the older ones are pushed upwards and become keratinised to form 
the root and shaft of the hair.

Hair pigments, like all other visible pigment in mammals, result from 
synthesis and distribution of melanin, in this case, in the hair bulbs. 
The melanins are produced in melanocytes from tyrosine and can be of two 
basic types: eumelanins, which are brown or black; and phaseomelanins, 
which are red or yellow. Black human hair contains approximately 99% 
eumelanin and 1% phaseomelanin, brown and blond hair contain 95% eumelanin 
and 5% phaseomelanin; and red hair contains 67% eumelanin and 33% 
phaseomelanin. However, The hair follicle and skin epidermal melanogenic 
systems are broadly distinct. The primary distinguishing feature of 
follicular melanogenesis, compared to the continuous melanogenesis in the 
epidermis, is the tight coupling of hair follicle melanogenesis to the 
hair growth cycle. The hair growth cycle consists of a growth phase 
(anagen) for 2-3 years, followed by a transitional stage (catagen) and 
resting phase (telogen), each of which lasts for about 2 weeks. On average 
about 85% of hairs are in anagen and hence actively growing. 
Hair follicle is a regenerating system. By traversing the phases of the 
cycle (growth, regression, resting, shedding, then growth again), the 
follicle demonstrates the unusual ability to completely regenerate itself. 
The basis for this regeneration rests in the unique follicular epithelial 
and mesenchymal components and their interactions. 

This hair growth cycle appears to involve periods of melanocyte 
proliferation (during early anagen), maturation (mid to late anagen) and 
melanocyte death via apoptosis (during early catagen). Thus, each hair 
cycle is associated with the reconstruction of an intact hair follicle 
pigmentary unit ellipsis at least for the first 10 cycles or so. 
Thereafter, grey and white hairs appear, suggesting an age-related, 
genetically regulated exhaustion of the pigmentary potential of each 
individual hair follicle. Melanocyte aging may be associated with reactive 
oxygen species-mediated damage to nuclear and mitochondrial DNA with 
resultant accumulation of mutations with age, in addition to dysregulation 
of anti-oxidant mechanisms or pro/anti-apoptotic factors within the cells.

Now how does “stress” relate to this? First of all, stress (e.g. fight, 
fright, flight, pain, hypoglycaemia, etc.) induce the secretion of 
adrenocorticotrophic hormone (ACTH) form the anterior pituitary 
profoundly. Indeed, the practical definition of a “stressful event” is 
anything that cause an increased secretion of ACTH. ACTH is a  peptide 
hormone synthesized as a pre-prohormone pro-opiomelanocortin (POMC). This 
large protein is processed in the anterior pituitary to form a number of 
peptide hormone, including ACTH, lipotrophic hormone, endorphins, and 
importantly melanocyte stimulating hormone (MSH). Thus when ACTH is 
secreted by the anterior pituitary, MSH is also secreted! MSH, as its name 
suggests, stimulate the melanocytes and cause them to form and distribute 
the pigment melanin. In fact, injection of MSH into a person 8-10 days can 
greatly increase darkening of the skin, esp. in light-skinned people. 
ACTH, because of its similarity to MSH, has about 1/30 as much melanocyte-
stimulating effect as MSH. Furthermore, because the quantities of pure MSH 
secreted in human being are extremely small, whereas those of ACTH are 
large, it is likely that ACTH normally is more important than MSH in 
stimulating melanocytes. 

Although I have not seen any research data confirming the causal 
relationship between stress, ACTH, and hair whitening, it is not difficult 
for one to speculate that under chronic stress, the body may respond to 
the “stress” by increasing secretion of ACTH. This increased ACTH level, 
if sustained for a prolonged period, may somehow over-stimulate the 
melanocytes in the hair bulb, and disrupt the normal coupling of 
follicular melanogenesis and hair growth cycle. This might then contribute 
to the age-related, genetically regulated exhaustion of the pigmentary 
potential of each individual hair follicle and subsequently resulting in 
hair whitening.

I hope this has shed some lights in how stress might relate to hair 
whitening.

Joshua Chai
Medical Student
University of Cambridge, UK

Reference:

1. Hearing VJ, Tsukamoto K, “Enzymatic control of pigmentation in 
mammals”, FASEB J 1991 Nov;5(14):2902-9
2. Borges CR, Roberts JC, Wilkins DG, Rollins DE, “Relationship of melanin 
degradation products to actual melanin content: application to human 
hair.”, Academic Press 2001
3. Tobin DJ, Paus R., “Graying: gerontobiology of the hair follicle 
pigmentary unit.”, abstract from PubMed
4. Stenn KS, Paus R., “Controls of hair follicle cycling.”, abstract from 
PubMed
5. Guyton & Hall, “Textbook of Medical Physiology”, Saunders