A prospective study of Quality of life in schizophrenia in three European countries

Abstract

Only a small number of studies have tried to identify factors influencing the subjective QoL of patients suffering from schizophrenia in a longitudinal design. These studies suffer from small clinical samples or compare baseline data only with a single follow-up. The European Schizophrenia Cohort Study overcomes these shortcomings by providing data from five time points on 1208 patients in psychiatric treatment in three European countries over a period of 2 years. QoL was measured with the brief version of Lehman's Quality of Life Interview. Random effects, between-effects and within-effects regression models were computed in order to measure the influence on subjective QoL of patients' socio-demographic and clinical characteristics and objective QoL. Objective QoL scores were generally found to be related to the equivalent subjective QoL scores. People's financial situation, and depressive and positive symptoms had a general effect on almost all subjective domains. The significant effects of objective finances on subjective domains like health and social relations raise interesting possibilities for intervention. Sufficient financial resources appear to be a necessary condition for achieving satisfactory QoL in schizophrenia patients. However, changes in individual's characteristics and circumstances did not relate as strongly as expected to changes in QoL, suggesting effective intervention may be difficult.

Introduction

In recent years the assessment of quality of life (QoL) has become an important indicator in psychiatric research of the functioning and well-being of people with schizophrenia (Meltzer, 1999). Born of the era of deinstitutionalization, QoL assessment provides an opportunity to describe the well-being of people with chronic mental illness living in the community in terms of a broad range of different domains, instead of focussing only on the patients' medical needs. QoL is thus typically defined as “… the multidimensional evaluation, by both intrapersonal and social-normative criteria, of the person-environment system of an individual in time past, current and anticipated” (Lawton, 1991). In order to develop intervention strategies capable of improving people's QoL, the investigation of deficits in several QoL domains provides a first step. The necessary second step is to identify the factors hampering the achievement of people's needs in different domains.

A number of potential influences have been examined in relation to the QoL of psychiatric patients. The intuitive assumption that objective living conditions modulate subjective QoL has been tested in a number of studies (Atkinson et al., 1997, Bechdolf et al., 2003, Ruggeri et al., 2001, Ruggeri et al., 2002). However, these found only weak to moderate correlations between objective and subjective QoL. Both aspects of QoL seem to be interrelated in a complex way, possibly as a result of adaptation processes influencing the subjective evaluation of objective living conditions (Franz et al., 2001). We have thus included objective QoL measures like contact with family or friends, daily activities and financial situation in our study. A person's social, occupational and psychological functioning is another ‘objective’ variable that is known to be associated with subjective QoL (Becker et al., 2005, Gaite et al., 2002). It was likewise included.

Other important influences on subjective QoL are the various symptoms of schizophrenia. Some cross-sectional studies (Carpiniello et al., 1997, Kasckow et al., 2001) have found only weak associations between severity of positive and negative symptoms of schizophrenia. Using longitudinal designs, Karow et al. (2005) found no significant association of positive symptoms with QoL, while van de Willige et al. (2005) in contrast found that the reduction of positive symptoms was the most important factor in improving QoL. Lehman (1983) reported a negative relationship between QoL and depression. Depression was the main explanatory factor in a study by Reine et al. (2003), with 22% of the variance of subjective QoL. Other studies also consistently show depression to be a predictor of subjective QoL in schizophrenia patients (Bengtsson-Tops et al., 2005, Sim et al., 2004).

The relationship between educational level and subjective QoL is ambiguous. Higher educational level was associated with greater general well-being in studies by Vandiver (1998) and Carpiniello et al. (1997), while Skantze et al. (1992), Ruggeri et al. (2005) and Caron et al. (2005a) reported the opposite relationship. Most studies on patients with schizophrenia have shown higher QoL in females (Atkinson et al., 1997, Carpiniello et al., 1997, Koivumaa-Honkanen et al., 1996). Increasing age is associated with better subjective QoL, particularly in the domain of finances (Caron et al., 2005b, Kearns et al., 1987, Mercier et al., 1998). Caron et al. (2005a) found a positive relation between overall lifetime duration of hospitalisations and QoL.

So far, relatively few longitudinal studies have addressed QoL in schizophrenia patients, and most have only compared baseline data with a single follow up (Fitzgerald et al., 2003, Galletly et al., 1997, Priebe et al., 2000, Ritsner et al., 2006, Ruggeri et al., 2001). Exceptions are Huppert and Smith (2001) with five, and van de Willige et al. (2005) with three assessment waves. However, these included only small clinical samples. Our analyses are based on data from the European Schizophrenia Cohort Study (Bebbington et al., 2005), a two-year follow-up study set in nine centres in Britain, France and Germany. The cohort comprised 1208 patients at baseline who were interviewed on five occasions at 6-monthly intervals.

Using this large data set, the present study aims to examine the influence of the afore-mentioned factors on schizophrenia patients' subjective QoL simultaneously. We are particularly interested in investigating how subjective QoL may be affected by intra-personal changes of these variables over time, as this might provide a basis for interventions to improve QoL in schizophrenia patients.