Problems with retrospective studies of the presence of schizophrenia.

Studies concerning the presence of schizophrenia in the distant past are controversial. Some authors maintain that schizophrenia-like illnesses existed in antiquity, while others argue that this is quite doubtful. Imprecise definition of schizophrenia, imposition of the current concept of schizophrenia onto the past, difficulties in interpreting ancient texts describing schizophrenia-like conditions, and cultural variables involved in the clinical definition of schizophrenia underlie these controversies. This article reviews the methodological issues that arise in such retrospective studies of schizophrenia.