"Shellshock was originally thought to be a physical phenomenon associated with (unspecified) damage to the brain due to "windage" of a near miss from a shell or blast of an explosion. Illogically it was also thought to be associated with being buried alive by the debris, or earth of an explosion. "It was not officially (administratively) recognised as a medical condition until the beginning of 1916 when a British army order stated that these cases were to be regarded as "wounded", not "sick" and the letter "W" was to be affixed by the MO of the unit to all such cases as being due to enemy action, as distinct from the letter "S" which meant "Sick Class" or due to accidents other than battle casualties. Specifically the order stated: "As the term "shell shock" has come to be vague and loosely applied to conditions which ought not to be returned as battle casualties, it has been decided to classify cases now returned "shell shock" as follows: (a) Suffering from Shock, Shell (b) Suffering from Concussion, Shell (c) Suffering from Burns." (DGMS June 1916.) "This is where it more or less stood until the appalling slaughter of the Battle of the Somme imposed even greater strains on the men and it became obvious that there was a great number of so-called "shell shock" cases. "In an effort to overcome the restrictions applied to the term "shell shock", MOs then applied other terms such as Neurasthenia, Battle exhaustion, Nervous exhaustion, Hysteria, Battle Shock, Nervous breakdown and "Functional" and this inevitably added to the confusion. "The soldiers themselves, however, were confronted with a new and mysterious form of injury called "Shell Shock" and a host of symptoms such as amnesia, anxiety, irritability, insomnia, flashbacks of the traumatic event, depression and alcoholism (probably as a form of self medication of the symptoms) were considered as being due to shell shock. "Since the Vietnam War, the term 'Shell Shock' has no longer been used and the symptoms described in the paragraph above are now classified as part of the condition of Post Traumatic Stress Disorder. "