Canities subita

Canities subita, also called Marie Antoinette syndrome or Thomas More syndrome, is an alleged condition of hair turning white overnight due to stress or trauma. The trivial names come from specific cases in history including that of Queen Marie Antoinette of France whose hair was noted as having turned stark white overnight after her capture following the ill-fated flight to Varennes during the French Revolution. An older case of Sir Thomas More's hair turning white the night before his beheading has also been recorded. Although a number of cases of rapid hair greying have been documented, the underlying patho-physiological changes have not been sufficiently studied.

Causes
The syndrome has been hypothesized to be a variant of alopecia areata diffusa or autoimmune non-scarring hair loss that selectively affects all pigmented hairs, leaving only the white hair behind. Canities subita is caused by high levels of emotional stress, which, in turn, causes less pigmentation of the hair. These form the basis of most uses of the idea in fictional works. It has been found that some hairs can become colored again when stress is reduced.

One study with experiments on mice found that stress caused white hair even if the immune system was suppressed (ruling out auto-immune response) and if the glands producing cortisol were removed. The study concluded that over-activation of the sympathetic nervous system was causing stem cells to stop producing pigment cells in hair follicles.

History
The earliest recorded claim of sudden whitening of the hair is represented in the Talmud in the story of a Jewish scholar who developed white hair at age 17 due to overwork. A contemporary case of accelerated hair-whitening has been documented in the medical journal Archives of Dermatology in 2009.

In popular culture
The condition has been featured in several works of fiction, characters afflicted by it include but are not limited to;
 * Jonathan Harker in Dracula. His hair turns from dark brown to white while listening to his wife Mina's account of Dracula assaulting her to turn her into a vampire.
 * Kaneki Ken from the manga and anime series Tokyo Ghoul, after undergoing days of torture at the hand of Jason, his naturally black hair turns stark white.
 * Hajime Nagumo, from the light novel and anime series Arifureta, his black hair turns white after he's forced to survive in a monster-infested dungeon for weeks and eat their poisonous flesh.
 * Dabi, from the manga and anime series My Hero Academia, born with a weak constitution, use of his quirk accelerated his body's deterioration and eventual pigment loss in his hair. Likewise, Tomura Shigaraki from the same series also developed this condition. However, his hair went from black to blue from the trauma of killing his family, to white after coming to terms with his trauma
 * Lagertha, from the History Channel series Vikings, season 5 Part 2
 * Leland Palmer from the TV series Twin Peaks
 * Jean Valjean from the book Les Misérables, from stress and inner turmoil
 * Toby from Sweeney Todd: The Demon Barber of Fleet Street, the musical by Stephen Sondheim
 * Zoidberg, from the animated sitcom Futurama. In the episode Möbius Dick, following an encounter with a four-dimensional space whale, the ordinarily hairless crustacean rapidly grows hair in order that it can immediately turn white from stress.
 * Louis, from the book Pet Sematary from grief and loss of sanity.