The idea that this set of symptoms forms a distinct entity began to attain greater recognition in the latter part of the 19th century. John Erichsen, a surgeon from London, played an important role in developing the study of PCS. The controversy surrounding the cause of PCS began in 1866 when Erichsen published a paper about persisting symptoms after sustaining mild head trauma. He suggested that the condition was due to "molecular disarrangement" to the spine. The condition was originally called "railroad spine" because most of the injuries studied had happened to railroad workers. While some of his contemporaries agreed that the syndrome had an organic basis, others attributed the symptoms to psychological factors or to outright feigning. In 1879, the idea that a physical problem was responsible for the symptoms was challenged by Rigler, who suggested that the cause of the persisting symptoms was actually "compensation neurosis": the railroads practice of compensating workers who had been injured was bringing about the complaints. Later, the idea that hysteria was responsible for the symptoms after a mild head injury was suggested by Charcot. Controversy about the syndrome continued through the 20th century. During World War I many soldiers with puzzling symptoms after being close to a detonation but without any evidence of a head wound. The illness was called shell shock, and a psychological explanation was eventually favoured. By 1934 the current concept of PCS had replaced ideas of hysteria as the cause of post-concussion symptoms.
With their focus on psychological factors, the ICD-10 criteria support the idea that the cause of PCS is functional. Like the ICD-10, the ICD-9-CM defines PCS in terms of subjective symptoms and discusses the greater frequency of PCS in people with histories of mental disorders or a financial incentive for a diagnosis.The DSM-IV lists criteria for diagnosis of PCD in people who have had a head trauma with persistent post-traumatic amnesia, loss of consciousness, or post-traumatic seizures. In addition, for a diagnosis of PCD, patients must have neuropsychological impairment as well as at least three of the symptoms marked with a check mark in the table at right under "DSM-IV". These symptoms must be present for three months after the injury and must have been absent or less severe before the injury. In addition, the patient must experience social problems as a result, and must not meet criteria for another disorder that explains the symptoms better.Neuropsychological tests exist to measure deficits in cognitive functioning that can result from PCS. The Stroop Color Test and the 2&7 Processing Speed Test (which both detect deficits in speed of mental processing) can predict the development of cognitive problems from PCS. A test called the Rivermead Postconcussion Symptoms Questionnaire, a set of questions that measure the severity of 16 different post-concussion symptoms, can be self-administered or administered by an interviewer. Other tests that can predict the development of PCS include the Hopkins Verbal Learning A test (HVLA) and the Digit Span Forward examination.