How many and which are the psychopathological dimensions in schizophrenia? Issues influencing their ascertainment

During the last two decades, much effort has been made to precisely characterize the symptom dimensions of schizophrenia. A number of dimensional models have been proposed, the most popular of which has been a three-dimensional model consisting of psychotic, negative and disorganizational symptoms. This model, however, has been criticized as too simplistic, and more complex models have been proposed, although to date there has been no consensus as to the number and nature of dimensions necessary to account for the whole range of schizophrenic symptoms. In the present paper, the authors review the main methodological issues which have led to the current confusion about the number of dimensions underlying schizophrenic psychopathology. Among the main issues influencing the delimitation of dimensions are: statistical procedures for determining the number of factors, phase of the illness, level of analysis of symptoms (i.e., symptoms or groups of symptoms), and measurement instrument used. Studies analyzing either a broad range of symptoms or particular symptoms at a finer level have produced a rather complex picture of schizophrenic dimensions. There is evidence supporting the existence of eight major dimensions of psychopathology: psychosis, disorganization, negative, mania, depression, excitement, catatonia and lack of insight. The dimensional structure of symptoms becomes even more complex if one considers that these big dimensions can be further divided into more elementary components. A hierarchical approach for organizing the complex dimensional structure of schizophrenic symptoms is proposed.