Negative symptoms: are they indigenous to schizophrenia?

The sudden popularity of positive and negative symptoms (PNS) has probably arisen as a result of the need for an instrument for clustering schizophrenic patients into subgroups that would respond similarly to the various treatments. The relation of PNS to the three major models for the etiology of schizophrenia (disease, socioenvironmental, and vulnerability) has been delineated. The question was raised regarding the indigenous nature of negative symptoms, their permanency, and whether they can be used to test the tenability of the three models. A strategy was suggested for determining whether the negative symptoms are permanent features of schizophrenia by providing techniques for attempting to eliminate them through therapeutic intervention. The need for developing operational criteria for the presence of each symptom was suggested to improve reliability of ratings, and construct validity designs were formulated for increasing their validity. The provision of a valid and reliable scale for negative symptoms and a scientific model for encompassing the various claims for negative symptoms is necessary before progress can be made.