CLINICAL HANDBOOK OF SCHIZOPHRENIA

57. Quality of Life 587FACTORS INFLUENCING QUALITY OF LIFEStudies have shown that patients with schizophrenia are frequently more satisfied withtheir lives than clinicians would objectively expect them to be given their poor living situation,and that they are also no more dissatisfied than members of other groups withphysical illnesses or social disadvantages. Schizophrenia often is a persistent conditionthat lasts for several decades. A high subjective quality of life despite poor living conditionsmay be explained by the relatively long duration of illness, which has given the patientstime to accept their chronic condition; to adjust their expectations of life, their stateof health, and their available resources; and to compare themselves to other patientsrather than to people from preillness peer groups. Yet, in addition to the length of illness,a number of other factors associated with subjective quality-of-life scores may be groupedinto sociodemographic and clinical domains.Sociodemographic FactorsLower quality of life is more likely to be reported by male patients with schizophreniawho are younger, have a high level of education, live alone, live in a less restrictive environment,and are not employed. However, these characteristics are not strong predictorsof subjective quality of life in clinical populations.Clinical FactorsSymptom level is the most important factor influencing subjective quality of life of patientswith schizophrenia. The higher symptom level is consistently associated with lower subjectivequality of life, explaining up to 30% of the variance (Kaiser et al., 1997). The associationis dominated mostly by mood, especially anxiety and depression symptoms. Indeed, depressionis the strongest variable associated with life satisfaction in psychiatric patients. Onthe individual-patient level, changes over time in subjective quality of life were found to correlatewith changes in anxiety and depression, suggesting that changes in depressive symptomsneed to be considered when interpreting changes in satisfaction with life (Fakhoury etal., 2002). The significant impact of mood on subjective quality of life suggests that any interventionto improve psychopathology may need to consider patients’ affective state,which is significantly related to their subjective quality of life. However, the direction of theinfluence can be questioned: Does depression influence the appraisal of life and lead to lessfavorable subjective quality-of-life scores? Or does the reverse occur, with a negative view oflife leading to more depressive symptoms? Or is the association more complex, so that bothdepression and subjective quality of life are determined by similar underlying cognitive andemotional processes? Research has not yet answered these questions. Clinical characteristicssuch as subclass of schizophrenia (e.g., paranoid schizophrenia), early onset of symptoms,previous hospitalization, and age at first hospitalization are negatively associatedwith subjective quality of life of patients with schizophrenia.QUALITY OF LIFE AS AN OUTCOME CRITERIONThe current prominence of quality of life stems from its frequent use as an outcome inclinical trials. However, it is a rather “distal” outcome, because the effect of most therapeuticinterventions on quality of life is likely to be indirect and evidenced at a later time.This is in contrast to “proximal” outcomes, such as symptoms, whose effect is likely tobe direct and immediate. Thus, the time it takes for an intervention to impact on quality-