Neurocognition and long-term prediction of quality of life in outpatients with severe and persistent mental illness
Introduction
Quality of life (QOL) has been described as “the richness of the individual's personal experience including his or her social, occupational, and interpersonal functioning” (Bow-Thomas et al., 1999). Although overlapping with measures of general community functioning, the QOL construct also includes subjective satisfaction of one's life (Lehman et al., 1995). QOL issues have been receiving more attention in persons with severe and persistent mental illness (SPMI) due to a shift in outcome focus from improving symptoms to a more holistic view of the impact psychiatric illness has on an individual's life (Hansson et al., 1999).
Studies of persons with SPMI report that QOL can be predicted by psychiatric symptoms including negative symptoms Norman et al., 2000, Cohen and Talavera, 2000, Bow-Thomas et al., 1999, Ho et al., 1998, positive symptoms Kasckow et al., 2001, Norman et al., 2000, Bow-Thomas et al., 1999, anxiety Huppert and Smith, 2001, Hansson et al., 1999, and depression Priebe et al., 2000, Hansson et al., 1999; quality of clinical treatment such as the presence of a therapeutic relationship (McCabe et al., 1999) and medication side effects (Ritsner et al., 2002); and psychosocial environmental factors such as a positive family interactions (Halford et al., 1991).
Intuitively, one characteristic that would appear to be associated with QOL in SPMI is neurocognition as it has been found to have important predictive validity for functional outcome in persons with SPMI (Brier et al., 1991). In a meta-analysis, Green et al. (2000) reported that outcome measures such as community functioning, social problem solving, and psychosocial skill acquisition can be predicted by vigilance, working memory, verbal memory, and executive functioning.
Studies examining the predictive validity of neurocognition on QOL, however, generally demonstrate weak to moderate correlations between different measures of neurocognition and QOL including verbal memory (−0.26) (Dickerson et al., 1998), span of apprehension (−0.37) and iconic memory (−0.43) (Helsegrave et al., 1997), vocabulary (0.29) (Addington and Addington, 2000), Digit Span (−0.25) (Smith et al., 1999), and Mini-Mental Status Examination scores (Kasckow et al., 2001). In the majority of these studies, a global quality of life index was used and many reported more significant associations with other measures including depression Dickerson et al., 1998, Smith et al., 1999, general psychopathology (Helsegrave et al., 1997), and positive and negative symptoms (Addington and Addington, 2000).
In another study with SPMI, executive functioning acted as a moderator variable for QOL (Brekke et al., 2001). Subjects with impaired executive functioning demonstrated a positive relationship between executive functioning and subjective experience (r=0.55 and 0.61). By contrast, SPMI subjects with intact executive functioning demonstrated a negative correlation between psychosocial functioning and self-esteem (−0.24) and satisfaction with life (−0.46).
The current study examines the long-term predictive validity of neurocognitive functioning for QOL in outpatients with SPMI. The purpose of the study is twofold. First, we attempt to examine the long-term effects of neurocognition on QOL. Unlike most QOL studies, the current study is a longitudinal study with outcomes measured more than 5 years after the collection of predictor variables. Second, we are interested in whether neurocognition can predict QOL in a predominantly ethnic minority SPMI sample. Although we do not have specific hypothesis about which cognitive variables will be important in predicting specific areas of satisfaction and functioning, we do predict that neurocognition in general will be significantly associated with QOL.
Section snippets
Sample selection/subjects
Subjects were procured from two sources, a statewide study of managed care versus fee-for-service treatment of adults with SPMI conducted in 1998 and a state hospital neuropsychology data base. The managed care study consisted of 563 SPMI patients who were randomly selected via computer. All patients were interviewed by trained graduate students and doctorates in psychology and social work and had been diagnosed with ICD-9 codes 295–298. The state hospital neuropsychological data base consisted
Results
Significant results were found for several BQOLI subscales (see Table 3). For the subjective scales, the following stepwise regression equations were significant: social relations (df=1, F=7.698; p<0.013) (r2=0.202) with Digit Span as the predictor variable in the following regression equation, y=20.35+−0.618x; family contact (df=1, F=6.728; p<0.015) (r2=0.194) with Finger Tapping total as the predictor variable, y=16+−0.067x; daily activities (df=1, F=10.05; p<0.004) (r2=0.264) using the WMSMQ
Discussion
Our findings supported the general hypothesis that neurocognition has long-term predictive validity for QOL in the SPMI population. This finding makes intuitive sense given that neurocognition has consistently been associated with overlapping outcome measures such as vocational success and independent living, as well as social problem solving skills and an ability to learn from rehabilitation modules that may impact QOL (for a review, see Green et al., 2000). Our results indicate that these
Acknowledgments
The authors would like to thank Tamra Rincon and Lisa Iguchi for their assistance in data procurement and management.
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