FROM SHELLSHOCK TO COMBAT STRESS: A COMPARATIVE HISTORY OF MILITARY PSYCHIATRY. Hans Binneveld, Amsterdam University Press, 1997.
p. 86 Dominant explanatory model of WWI period was bio-medical or somatic--"mental illness was conceived as a disease of the brain...due t physical injuries, which resulted in behavioral disorders." Culprits were thought to be excessive use of alcohol, venereal diseases, hereditary weakness such as a "weak constitution" or "nervousness."
p. 87 "The [British] War Office Committee of Inquiry Into Shell Shock" met 1920. "Doctors...expressed their doubts regarding the military capacities of the Jews and the Irish, for example" thus assigning "hereditary weakness" to certain ethnic groups. Many doctors thought their patients were "weaklings...or tricksters."
p. 89 Another cause of shell shock was thought to be "unresolved psychic conflicts in the mind of the soldier." Freud was of this school.
By the end of WWI, doctors still argued whether the cause of shell shock was physical or psychological.