[The advantage of a modern operational approach to the diagnosis of mental disorders. The case of the Bavarian King Ludwig II--an example from biographical research].

Worldwide discrepancies in the classification, terminology and diagnosis of mental disorders have induced efforts for unification after World War II. This led to the introduction of an operational diagnostic approach according to strict criteria, at the same time taking into account the comorbidity of disorders. However, this approach is still not routinely used. The consequences of this deficiency are demonstrated here by an example from biographical research referring to the Bavarian King Ludwig II. The study is based on an extensive search of the relevant literature. Although the pathography of this Bavarian king is well documented, the diagnoses published between 1910 and 2010 by altogether 21 specialists, are distributed rather chaotically over 24 diagnostic categories of the ICD-10. Merely in the (probably wrong) diagnosis of a schizophrenic psychosis is there agreement among half of the authors. This is concordant with the expert diagnosis of paranoia by von Gudden and his colleagues (1886) when considering the then contemporary concept of the disorder. According to modern diagnostic principles almost half of the 24 diagnoses can be confirmed. The others have to be regarded as false diagnoses. The conclusion is that modern principles of the diagnosis of mental disorders should be applied according to internationally accepted diagnostic manuals. This approach should be used in, but is not exclusive to, biographical research. Precondition is, of course, the exact knowledge and careful application of these principles.