Negative symptoms of schizophrenia: new developments and unanswered research questions.

Negative symptoms of schizophrenia are associated with poor functional outcome and place a substantial burden on people with this disorder, their families, and health-care systems. We summarise the evolution of the conceptualisation of negative symptoms, the most important findings, and the remaining open questions. Several studies have shown that negative symptoms might be primary to schizophrenia or secondary to other factors, and that they cluster in the domains of avolition-apathy and expressive deficit. Failure to take this heterogeneity into account might hinder progress in research on neurobiological substrates and discoveries of treatments for primary or enduring negative symptoms. Improvement in recognition and routine assessment of negative symptoms is instrumental for correct management of secondary negative symptoms that are amenable to treatment. If substantial progress is to be made in the understanding and treatment of negative symptoms, then advances in concepts and assessment should be integrated into the design of future studies of these symptoms.