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Revisiting the U.S. Navy Submarine Service Psychological Casualty Rate in World War II

Conclusions concerning how many World War II U.S. Navy submariners should be classified as psychiatric casualties have long been based on a pioneering study by two navy physicians, Commander Ivan Duff, MD, and Captain Charles Shilling, MD, that was first made public in the Journal of the American Psychiatric Association shortly after the war. This article seeks to show that, despite the longevity of the resulting published figures, there were serious problems in their approach and conclusions. The data set of the study was far from comprehensive, which, in turn, led to erroneous calculations generating a minuscule number—approximately two cases per 1,000 submariners—that in turn necessitated explanatory overreach. Reasons for the approach taken in the original work, and subsequent longevity of acceptance and celebration of the results produced, are then examined through the lens of confirmation bias.