Measures and Conceptualizations of Symptoms in Schizophrenia

Schizophrenia presents as a heterogenous disorder characterized by diverse expression of symptoms between individuals. Thus, clinicians and researchers rely on comprehensive symptom measures for diagnosis and treatment. This dissertation investigated two symptom measures, the Positive and Negative Syndrome Scale (PANSS; Kay, Fiszbein, & Opler, 1987), a commonly used scale that assesses a broad range of symptoms of schizophrenia, as well as the Brief Negative Symptom Scale (BNSS; Kirkpatrick et al., 2011; Strauss et al., 2012), a novel scale that focuses on the assessment of five negative symptom domains (i.e., anhedonia, asociality, avolition, blunted affect, and alogia). The first study of this dissertation included PANSS data collected from individuals with schizophrenia who were evaluated for the National Institute of Mental Health Clinical Antipsychotic Trials of Intervention Effectiveness. Confirmatory factor analysis findings indicated that a five-factor structure (i.e., positive, negative, disorganized, excited, and depressed factors) was superior compared to other models for both females and males, and at two time points, indicating that the latent symptom structure is likely stable across sexes and over time, and providing support for the longitudinal application of the PANSS for both sexes. The second and third studies examined the BNSS and included individuals with schizophrenia who were evaluated at several outpatient facilities. The second study found unique patterns of correlations among the five negative symptom domains with neurocognition and community-based psychosocial functioning, supporting external validation of the five-factor negative symptom model. Findings of the third study revealed that, when submitting the five negative symptom domains to a cluster analysis, a four-cluster solution emerged including clusters with low negative symptoms, severe negative symptoms, as well as two clusters with medium-range symptoms, one with predominantly elevated blunted affect and one with elevated avolition, providing new insight into the now century-long pursuit to better explain symptom heterogeneity of schizophrenia. The second and third study imply revisions to the DSM-5 and development of new treatments targeting the five negative symptom domains. Taken together, the current results provide a number of new insights into symptoms of schizophrenia (and possibly other psychotic disorders). Symptom constructs appear comparable for females and males across time and there is substantial support for new conceptualization of negative symptoms, including validity evidence supporting the five negative symptom domains and their usefulness in identifying subgroups of schizophrenia that differ along important demographic, clinical, neurocognitive, and functional dimensions. These insights inform schizophrenia symptom conceptualizations and the use of symptom measures