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In the 19th century, with the development of railway transportation, train accidents became a frequent source of death and serious injury.
Some of the victims claimed injury following an accident without a visible pathology. Jon Eric Erichsen, a British surgeon, in 1867 published a book called On Railway and Other Injuries of the Nervous System in it he argued that an unseen physical injury to the spine and brain caused the condition `railway spine.'
Railway spine was a concept that rooted the illness to the body and not the mind thus making it more legitimate and avoided stigma of mental illness.
Later, work by Jean-Martin Charcot, Piere Janet and Freud established the idea that overwhelming events can cause mental disorders.
Before WWI the terms "soldiers'heart," "war neuroses" and "general nervous shock" were used to refer to the psychological casualties of combat. During WWI the term "shell shock" became widely accepted as it avoided the term hysteria. During World War II the U.S. military used the term "operational fatigue" or more often "combat fatigue."
Google scanned entire libraries and converted the text into a massive database and now they have created a viewer that allows you to search for phrases and display how those phrases have occurred in a corpus of books (e.g., "British English", "American English, etc..) over several years.
I searched for railway spine vs. shell shock vs. combat fatigue vs. PTSD.
Posttraumatic stress disorder was formally recognised and introduced to DSM-III in 1980, this was at a time that the psychological impact of the war on Vietnam war veterans was an issue of big public debate in the US and women's groups started speaking out against domestic violence and rape.