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Edited by
Andrea Fiorillo, University of Campania “L. Vanvitelli”, Naples,Peter Falkai, Ludwig-Maximilians-Universität München,Philip Gorwood, Sainte-Anne Hospital, Paris
Schizophrenia is a disabling and complex mental disorder that has a negative impact on the real-life functioning of people suffering from this disease, with a consequent huge burden on patients, on their families, and on the healthcare system. Despite the available interventions, only about 15% of subjects with schizophrenia meet the criteria for recovery. This might be due to the fact that available treatments do not satisfactorily target aspects that greatly influence schizophrenia functional outcome, such as negative symptoms and cognitive impairment. Despite the broad consensus on the definition of different negative symptom and cognitive function domains, these aspects are not always assessed in line with current conceptualization, and they are still poorly recognized and often neglected by physicians, family members/caregivers, and the patient himself/herself as they cause much less concern than other clinical features. In this chapter we focus on negative symptoms and cognitive impairment as the two most neglected schizophrenia dimensions in terms of assessment and treatment; we also provide an update of preclinical and clinical research and its relevance to clinical and research practice, and suggest future directions in the field.
The conceptualization of negative symptoms (NS) in schizophrenia is still controversial. Recent confirmatory factor-analytic studies suggested that the bi-dimensional model (motivational deficit [MAP] and expressive deficit [EXP]) may not capture the complexity of NS structure, which could be better defined by a five-factor (five NS domains) or a hierarchical model (five NS domains as first-order factors, and MAP and EXP, as second-order factors). A validation of these models is needed to define the structure of NS. To evaluate the validity and temporal stability of the five-factor or the hierarchical structure of the brief negative symptom scale (BNSS) in individuals with schizophrenia (SCZ), exploring associations between these models with cognition, social cognition, functional capacity, and functioning at baseline and at 4 years follow-up.
Methods
Clinical variables were assessed using state-of-the-art tools in 612 SCZ at two-time points. The validity of the five-factor and the hierarchical models was analyzed through structural equation models.
Results
The two models had both a good fit and showed a similar pattern of associations with external validators at the two-time points, with minor variations. The five-factor solution had a slightly better fit. The associations with external validators favored the five-factor structure.
Conclusions
Our findings suggest that both five-factor and hierarchical models provide a valid conceptualization of NS in relation to external variables and that five-factor solution provides the best balance between parsimony and granularity to summarize the BNSS structure. This finding has important implications for the study of pathophysiological mechanisms and the development of new treatments.
The structure of negative symptoms of schizophrenia is still a matter of controversy. Although a two-dimensional model (comprising the expressive deficit dimension and the motivation and pleasure dimension) has gained a large consensus, it has been questioned by recent investigations.
Aims
To investigate the latent structure of negative symptoms and its stability over time in people with schizophrenia using network analysis.
Method
Negative symptoms were assessed in 612 people with schizophrenia using the Brief Negative Symptom Scale (BNSS) at baseline and at 4-year follow-up. A network invariance analysis was conducted to investigate changes in the network structure and strength of connections between the two time points.
Results
The network analysis carried out at baseline and follow-up, supported by community detection analysis, indicated that the BNSS's items aggregate to form four or five distinct domains (avolition/asociality, anhedonia, blunted affect and alogia). The network invariance test indicated that the network structure remained unchanged over time (network invariance test score 0.13; P = 0.169), although its overall strength decreased (6.28 at baseline, 5.79 at follow-up; global strength invariance test score 0.48; P = 0.016).
Conclusions
The results lend support to a four- or five-factor model of negative symptoms and indicate overall stability over time. These data have implications for the study of pathophysiological mechanisms and the development of targeted treatments for negative symptoms.