Negative symptoms of schizophrenia: clinical features, relevance to real world functioning and specificity versus other CNS disorders.

Negative symptoms have long been recognized as a central feature of the phenomenology of schizophrenia, dating back to the early descriptions by Kraepelin and Bleuler. Over the ensuing century, there have been important clarifications and reconceptualizations regarding the phenomenology of negative symptoms in schizophrenia. This review explores these developments, including the delineation of two underlying subdomains of negative symptoms - amotivation (i.e., avolition/apathy and asociality) and diminished expression (i.e., poverty of speech and affective flattening). Further, advances in our understanding of specific motivational and hedonic deficits seen in schizophrenia are explored. The findings that negative symptoms stand apart from depressive and cognitive symptoms in schizophrenia are also discussed. In terms of the predictors of functional outcomes in schizophrenia, we explore both the direct role of negative symptoms in this regard, as well as their indirect role through cognition. We then broaden our examination of negative symptoms to related disorders across the schizophrenia spectrum, as well as to other neuropsychiatric illnesses, where negative symptoms have been increasingly recognized. We explore the differential characteristics of negative symptoms across these illnesses, and their relevance to functional outcomes. This transdiagnostic presence and relevance of negative symptoms highlights the need for continued exploration of their phenomenology and neurobiology as we move to develop effective interventions to address these debilitating symptoms and improve functional outcomes.