The concept of post-traumatic stress disorder (PTSD) was to be verified considering World War I soldiers suffering from psychiatric and neurologic diseases. According to hypotheses, relevant circumstances of the case history and significance of the direct military action had to be examined. In 2002, medical histories dating from 1914 to 1921 of male soldiers in Jena, Germany, were analyzed. Statistical examination carried out by means of the chi2 test revealed mental illness more frequently in soldiers with relevant family anamnesis, previous psychiatric treatment, or degree of voluntariness than in soldiers not so characterized. The accumulation of mental illnesses was lower in soldiers involved in military actions or directly with firing weapons than in soldiers never involved in battles. These results are in accord with historical but not current literature on PTSD. The author is of the opinion that psychiatric anamnesis is not given enough consideration in the concept of PTSD.