Quality of life in stable schizophrenia: The relative contributions of disorganization and cognitive dysfunction

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Abstract

Objective

The purpose of this study was to examine the relative contributions of disorganization and cognitive dysfunction to quality of life (QOL) in patients with stable schizophrenia.

Methods

A total of 276 consecutive outpatients with stable schizophrenia were enrolled in a cross-sectional study. We performed a mediation analysis to assess the specific effect of disorganization on QOL, as assessed by the Heinrichs–Carpenter Quality of Life Scale (QLS), and the possible mediating role of cognitive dysfunction.

Results

Our findings were as follows: (i) disorganization was negatively related to the total QLS score; (ii) disorganization was negatively related to two of the four QLS domains, namely the role-functioning domain (occupational/educational) and the intrapsychic functioning domain (e.g., motivation, curiosity, and empathy); and (iii) verbal memory was a partial mediator of the relationship between disorganization and QLS (the total score and the two above-mentioned domains).

Conclusions

Disorganization demonstrated direct and indirect effects via verbal memory on two domains of functioning, as measured by the QLS. These results highlight the importance of improving disorganization and cognition (particularly verbal memory) to improve the functional outcomes of patients with schizophrenia.

Introduction

Regarding the factors that influence quality of life (QOL) in patients with schizophrenia, the majority of researchers have primarily focused on psychiatric symptoms, although many other influential predictors have been identified (Eack et al., 2007). Indeed, one factor that has been shown to be consistently negatively associated with QOL is psychopathology (Lambert and Naber, 2004). QOL has been negatively correlated with positive, negative, and general psychopathology, as well as with depressive symptoms; some studies have found a large relationship between these measures (Norman et al., 2000, Fitzgerald et al., 2001, Rocca et al., 2005), while other studies have identified only a small to moderate relationship (Sim et al., 2004, Ritsner et al., 2005). In many of these studies, positive symptoms, such as hallucinations and delusions, were combined with conceptual disorganization to form a positive symptom factor. Over time, several factor-analytic studies (Norman et al., 1997, Meagher et al., 2000) have supported the view that delusions and hallucinations are distinct from positive symptoms, such as formal thought disorders. As a result, disorganization has emerged as a separate domain worthy of consideration. Disorganization was introduced by Liddle (1987) as an important third factor in addition to the positive and negative symptom factors. According to Liddle, schizophrenic symptoms segregated into three syndromes: psychomotor poverty (poverty of speech, lack of spontaneous movement and various aspects of blunting of affect); disorganization (inappropriate affect, poverty of content of speech, and disturbances of the form of thought); and reality distortion (particular types of delusions and hallucinations). Some studies have suggested that disorganization may be a stronger predictor of community function than reality distortion (Norman et al., 1999, Ventura et al., 2009).

Much more attention has been paid to cognitive dysfunction because it may lead to poor community functioning, including social functioning, work performance, and social skills (Bryson and Bell, 2003). Cognitive deficits persist throughout the illness and serve as rate-limiting factors associated with functional recovery (Keefe and Fenton, 2007). Studies investigating the ability of neurocognitive variables to predict QOL in individuals with schizophrenia have yielded conflicting results. However, a recent meta-analysis revealed a markedly different relationship between neurocognition and objective and subjective QOL (Tolman and Kurtz, 2012). Small to moderate relationships (d  0.55) were found between crystallized verbal ability, working memory verbal list learning, processing speed, and the executive function and objective indices associated with QOL. In contrast, the results revealed either nonsignificant or inverse relationships for the vast majority of neurocognitive measures and measures of subjective QOL.

Concerning the relationships between cognition and symptoms, there is evidence in the literature of strong correlations between performance on neurocognitive tests and negative symptoms (Ventura et al., 2009). Differential relationships between positive symptoms and neurocognitive functioning have been reported. Symptoms of disorganization, when reported as a factor separate from reality distortion, appear to be related to neurocognition and warrant a separate empirical study. A recent meta-analysis demonstrated a small to moderate (r =  0.23) relationship between disorganization and neurocognition, while the relationship between neurocognition and reality distortion was relatively weak (r =  0.04). Disorganization was related to all of the domains of cognitive functioning examined, including verbal memory (r =  0.20), attention/vigilance (r =  0.25), reasoning and problem solving (r =  0.24), processing speed (r =  0.26), visual memory (r =  0.20), and working memory (r =  0.20). In contrast, reality distortion showed no such broad association (r values ranging from − 0.01 to − 0.12) (Ventura et al., 2010).

Previous research has linked disorganization to neurocognition and neurocognition to QOL, although in separate studies. The present study was conducted to determine whether the relationship between disorganization and QOL may be mediated by the extent of cognitive deficits in patients with schizophrenia.

Thus, the objectives of the current study were three-fold. First, we investigated the ability of disorganization alone to predict QOL. Given the previous contradictory findings in the literature, we intended for this investigation to be an exploratory analysis and expected that the disorganization would predict a significantly lower QOL. Second, we studied the ability of cognition alone to predict QOL. Given the results of previous studies, we anticipated a role for cognition in the prediction of QOL. Third, we explored the possibility that disorganization continues to predict QOL when cognition is also considered. It was expected that both disorganization and neuropsychological deficits interact to influence QOL, with neuropsychological deficits acting as partial mediators of the relationship between disorganization and QOL.

Section snippets

Participants

This study was conducted at the Department of Neuroscience, Psychiatric Section, and the Department of Mental Health ASL TO1 Molinette-Turin, Italy. Between July 2008 and March 2010, we screened 345 schizophrenia spectrum patients of either gender, aged between 18 and 65 years. A total of 276 consecutive outpatients who met the inclusion criteria and agreed to participate in the study were enrolled. They all fulfilled the formal Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-TR) (

Results

The patients in our study had DSM IV-TR schizophrenia diagnoses of the paranoid subtype (n = 158, 57%), disorganized subtype (n = 27, 10%), undifferentiated subtype (n = 57, 21%), or residual subtype (n = 34, 12%). The mean age (± S.D.) of our patients was 40 (± 10.8) years. The mean duration of illness (± S.D.) was 14.2 (± 9.74) years. There were 116 females (42%) and 160 males (58%). Sixty-two percent of patients were treated with second-generation antipsychotics (SGAs), and 38% were treated with

Discussion

The purpose of the present study was to examine the interactions between disorganization and cognition in predicting QOL within a sample of outpatients with stable schizophrenia.

First, as hypothesized, disorganization was negatively related to QOL. In the literature, there is evidence that disorganization is the most reliable predictor of a variety of outcome indicators (Heslegrave et al., 1997, Norman et al., 1999, Smith et al., 1999, Ventura et al., 2009). Recently, Ventura et al. (2010)

Role of the funding source

This study was supported by research grant 2006–2167 by the Compagnia di San Paolo, Torino, Italy and by a research grant by the Fondazione Cassa di Risparmio di Savigliano, Savigliano, Torino, Italy.

Contributors

MS, GR and PR designed the study and wrote the protocol. BC, FC, MG and CM carried out the patient clinical assessment and recruitment, data collection and analysis. CM and MS wrote the first draft of the manuscript. All authors contributed to and have approved the final manuscript.

Conflict of interest

We wish to confirm that there are no known conflicts of interest associated with this publication and there has been no significant financial support for this work that could have influenced its outcome.

We confirm that the manuscript has been read and approved by all named authors and that there are no other persons who satisfied the criteria for authorship but are not listed. We further confirm that the order of authors listed in the manuscript has been approved by all of us.

We confirm that we

Acknowledgments

This study was supported by the research grant 2006–2167 by Compagnia di San Paolo, Torino, Italy and by a research grant by the Fondazione Cassa di Risparmio di Savigliano, Savigliano, Torino, Italy.

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