Assessing the effects of atypical antipsychotics on negative symptoms. Collaborative Working Group on Clinical Trial Evaluations.

Attempts to clarify the domains of schizophrenia gained importance when the atypical antipsychotics joined the armamentarium of schizophrenia treatments because of evidence that these agents are superior to conventional antipsychotics for the treatment of negative symptoms. Negative symptoms can be divided into 3 components: (1) deficit or primary enduring negative symptoms that may or may not respond to treatment, (2) primary nonenduring negative symptoms, and (3) secondary negative symptoms that are associated with positive symptoms, extrapyramidal symptoms, depression, and environmental deprivation. The atypical antipsychotics have generally been found to be more effective than conventional antipsychotics against the totality of negative symptoms, but their effects on specific components are still under study. Sophisticated statistical tools such as path analysis have been used in investigations of the direct and indirect effects of atypical antipsychotics on negative symptoms, but these tools have limitations. Future study is needed to identify specific components of negative symptoms that may respond preferentially to one or another of the atypical antipsychotics.