QoL is emerging as an important outcome of the treatment of schizophrenia, yet relatively little is known about the factors that influence the QoL of individuals who suffer from this illness. The relationship between psychiatric symptoms and QoL among individuals with schizophrenia has been studied most extensively. However, this research has yet to elucidate how important psychiatric symptoms are to QoL, and which symptoms hold the strongest relations to QoL. To our knowledge, this is the first systematic meta-analysis to examine the effects of any potential contributor to QoL in schizophrenia. The results of this analysis suggest that psychiatric symptoms have a significant, but small, negative relationship with QoL in schizophrenia, with general psychopathology consistently emerging as the strongest contributor to poor QoL. In addition, findings suggest that positive and negative symptoms are not related to the QoL of all groups of individuals with schizophrenia equally, but that such symptoms may be particularly detrimental to QoL in studies of individuals receiving treatment in the community, and that positive symptoms are only weakly related to QoL in studies of individuals in the early course of the illness. Such findings hold several important implications for treatment development and future QoL studies in schizophrenia research.
First, given that general psychopathology shows the strongest relationship with QoL, this suggests that nonpsychotic signs and symptoms are important targets for treatments aiming to improve QoL for individuals with schizophrenia. Previous research has suggested that the strong correlations observed between measures of general psychopathology and QoL might be the result of subjective ratings being unduly influenced by mood.17,47
As such, it has not been clear whether such symptoms simply contaminate some forms of QoL measurement or should, in fact, be legitimate targets for QoL treatments. This research lends support to the latter, because both subjective and objective indicators of QoL were similarly and consistently most strongly related to general psychopathology. Unfortunately, while considerable progress has been made over the past 2 decades in developing effective pharmacological and/or psychosocial treatments for nonpsychotic psychopathology, principally anxiety and depressive symptoms, their optimal methods of use for individuals with schizophrenia have not been clearly identified.48
Further, much less attention has been paid to treatment of the secondary psychological effects of living with a chronic disability, such as schizophrenia.49
While our research does not identify a causal link between symptoms of general psychopathology and poor QoL in schizophrenia, it does suggest that identifying optimal methods of managing co-occurring nonpsychotic signs and symptoms, as well as the secondary effects of schizophrenia on psychological health may be particularly fruitful avenues for improving QoL among this population.
Additionally, this research points to the need for any QoL treatment to attend to both the patient's environment and stage of illness, because the relationships between some psychiatric symptoms and QoL varied significantly across these patient characteristics. In this research, we found that studies of individuals receiving treatment in the community showed significantly stronger negative relationships between positive and negative symptoms and QoL, compared with studies of individuals in inpatient settings. This pattern is congruent with the only known study to examine the moderating influence of the patient's environment on the effects of psychiatric symptoms on QoL32
and suggests that positive and negative symptoms may be most disabling for those living in the community. This is not surprising, given that most inpatient units are specifically designed to accommodate such symptoms, whereas in the community these symptoms pose substantial threats to social adjustment and functioning.50,51
The functional threats these symptoms present to individuals attempting to build a life in the community could substantially stifle progress on social, work, and life goals that would result in poorer QoL.
It is interesting that length of illness also moderated the relationship between positive symptoms and QoL, but that contrary to our expectations, studies of individuals in the early course of schizophrenia showed no significant relationship between positive symptoms and QoL. There may be a number of different reasons for this finding that concern how individuals who develop schizophrenia adjust to the onset of positive symptoms; however, because individuals experiencing a first episode of schizophrenia usually present in inpatient settings, the attenuated relationship between positive symptoms and QoL may simply reflect the diminished influence these symptoms hold to the QoL of individuals living on inpatient units. Unfortunately, because first-episode and inpatient studies were completely collinear in this research, we are unable to conclude whether the reduced relationship between positive symptoms and QoL in first-episode schizophrenia is due to treatment setting or the recent onset of the illness. Future research is needed to disentangle this issue by focusing on the determinants of QoL among individuals in the early course of schizophrenia living in the community.
Further, although this research indicates that psychiatric symptoms have a significant negative relationship with QoL in schizophrenia, the magnitude of this relationship is not large. For example, even general psychopathology that was most strongly related to QoL, explained no more than 12% of the variance in composite QoL scores. When only longitudinal studies were considered, general psychopathology explained less than 8% of the variance in QoL. Although this finding supports the discriminant validity of the concept of QoL in schizophrenia research, it underscores the need for further investigation into the psychosocial influences of QoL in schizophrenia and points to the importance of developing psychosocial approaches to help these individuals achieve more satisfying lives. An emerging literature of these influences suggests that helping individuals with schizophrenia build broader networks of support and meet their basic needs are promising starting points for treatments targeting QoL.29
Although pharmacological therapies that result in symptom reduction can produce important improvements in health-related QoL,52
psychosocial treatments are likely to be particularly well-suited to help improve the broader dimensions of QoL through enhancing a person's social support system or assisting in the meeting of basic needs. This is reflected in the broad improvements in QoL that have been found to result from some trials of psychosocial treatments that target these outcomes, such as case management services53–55
and peer support programs.56
While there is a clear need for future research to continue elucidating the effects of psychosocial treatments on the different domains of QoL, such findings suggest an important role for psychosocial approaches in improving QoL in schizophrenia. Consequently, as future research clarifies the prominent psychosocial influences of QoL, it will be important to direct these findings toward the development of psychosocial treatments targeted specifically at improving QoL for this population.
Finally, this research points to the relevance of several methodological characteristics that need to be attended to when designing and reporting on future studies of QoL in schizophrenia research. To begin, given that general psychopathology shares a modest amount of variance with all indicators of QoL, it will be important for future QoL studies to account for this overlap during study design and analysis. This is particularly important for future treatment studies, as before treatment effects can be interpreted as improvements in QoL, they need to be distinguished from improvements in general psychopathology. Further, there is a clear need for future longitudinal studies of the determinants of QoL in schizophrenia, because we found that cross-sectional studies tended to significantly overestimate the predictive utility of symptomatology. Unfortunately, to date, few longitudinal studies have examined the determinants of QoL in schizophrenia, particularly with regard to psychosocial determinants. Such studies are vital to the identification of the key determinants of QoL in schizophrenia and the mechanisms by which such determinants influence QoL, as well as the development of targeted approaches to improve QoL among this population. Lastly, future QoL studies will need to ensure that their samples are homogeneous with regard to stage of illness and treatment setting or specifically account for the differential relationships that are likely to occur across these factors between QoL and other constructs under investigation. In our review of the literature, we found that it was not uncommon for studies to contain mixed samples of inpatients and outpatients or early course and chronic patients. However, as our results show, there are systematic differences in how the dimensions of QoL interact with psychiatric symptoms among these samples, and ignoring these differences would obscure results. Consequently, future studies of the relationship between psychiatric symptoms and QoL will need to gather homogeneous samples, block on treatment setting and course of illness, or statistically account for these factors in moderator analyses, in order to accurately represent their results.
It is important to note that although these findings hold implications for treatment development efforts and future QoL research, this research also has a number of limitations that need to be recognized and addressed in future studies. First, it is important to remember that the unit of analysis in a meta-analytic study is research results and not individuals.37
As such, moderators of the effects of psychiatric symptoms on QoL cannot be interpreted at an individual level, rather such moderators must be understood as explaining variation among studies. Consequently, implications derived from moderator analyses need to be tested within studies of individuals in order to confirm these findings. Second, because of the relatively small number of studies that examined specific indicators of QoL (eg, subjective QoL) within certain moderator cells (eg, outpatient samples), it was necessary to conduct moderator analyses on composite QoL scores. This precluded us from examining how different indicators of QoL are moderated by different study characteristics. Such an analysis is likely to further clarify for whom psychiatric symptoms hold the largest threat to QoL, because these indicators are conceptually distinct and may react differently to symptoms among various patient populations. Future research will need to explicitly examine this issue by utilizing measures of QoL that contain multiple indicators, such as the Lehman Quality of Life Interview.28
Third, it is important to remember that many measures of health-related QoL include symptom measures as well, which may explain why psychiatric symptoms were most strongly related to health-related QoL. As such, effects regarding the relationship between psychiatric symptoms and health-related QoL need to be interpreted with caution, and future research will need to control for shared variance between psychiatric symptoms and symptom components of health-related QoL when examining these effects. Unfortunately, to date, most health-related QoL measures commingle mental and physical health symptoms in their measurement and scoring strategies that precludes meta-analytic techniques from disaggregating these effects. Fourth, it should be recognized that although the 4 dimensions of QoL examined in this research were derived from an extensive review of the literature, this 4-factor structure has yet to be subjected to empirical examination. Consequently, the distinctiveness of these dimensions of QoL continues to remain unclear, and future factor-analytic investigations are needed to elucidate the latent structure of the QoL construct. Finally, although general psychopathology appears to have the strongest relationship with QoL, because the heterogeneity of symptoms that fall within the omnibus “general psychopathology” category, the relative contribution of different nonpsychotic symptom domains to QoL is not clear from this research. Some research has suggested that symptoms of anxiety may be the most important to QoL,57
although few investigations have examined the independent influence of anxiety and other forms of general psychopathology on QoL within a single study. Additionally, while it is clear that general psychopathology is negatively related to QoL, this relationship cannot be assumed to be unidirectional (as having a poorer QoL is likely to have negative psychological consequences) and the reasons why such symptoms pose a larger threat to QoL in schizophrenia than the cardinal symptoms of the illness are not clear. Future longitudinal research is needed to clarify the relative predictive importance and reciprocal influence of different components of general psychopathology on QoL in schizophrenia, as well as to understand the mechanisms by which such symptoms influence QoL. Addressing these issues will provide important information about the determinants of QoL in schizophrenia and point to the methods that can be employed to help these individuals lead fuller and more satisfying lives.