Depressive symptoms in stable chronic schizophrenia: prevalence and relationship to psychopathology and treatment

Abstract

The prevalence and correlates of the depressive syndrome were explored in a population of 120 patients with stable, chronic schizophrenia living in the community. The presence of clinically significant depressive symptoms was defined by a score of 17 or greater on the Beck Depression Inventory. Patients were examined to assess severity of schizophrenic symptoms and medication side-effects. Sixteen of the 120 patients (13.3%) had significant depressive symptoms. Depressive symptoms were significantly correlated with the hostility/suspiciousness (P<0.0001), the positive symptom (P=0.0009) factor of the BPRS and with scores on the Significant Others Scale, a measure of patients' perceived lack of social support (P=0.0004). The association between depression and akathisia approached significance (P=0.007). There was no correlation with demographic variables, alcohol intake, antipsychotic dosage or anticholinergic dosage. Using a scale that rates the subjective aspects of the depressive syndrome, we found no evidence of a relationship between depression and negative symptoms in this population. These results indicate that persistent depressive symptoms in stable patients in the community are related to the degree of persistent positive psychotic symptoms, patient perceptions of social support and, weakly, to the degree of akathisia but not other aspects of antipsychotic treatment.

Introduction

It has been recognised for many decades that depression of mood is a frequently occurring symptom in schizophrenia. Although Kraepelin (1917) used prominent affective symptoms as one criterion with which to separate dementia praecox and manic-depressive illness, he also identified several depressive subtypes of schizophrenia. Eugen Bleuler (1950) considered depression to be part of the core symptomatology of schizophrenia. While it is generally recognised that depression of mood is common in schizophrenia and is an associated risk factor for death by suicide (Roy, 1986), there is little agreement on its aetiology.

Depressive symptoms are most frequently associated with the acute phase of the illness, with studies suggesting a point prevalence as low as 22% (House et al., 1987) and as high as 80% (World Health Organisation, 1973). Lower rates of depressive symptoms are seen in the chronic phase of the illness, with a range of 4% (Addington et al., 1992) to 25% (Knights et al., 1979) and an estimated mean, for chronic in-patients, of 15% (Leff, 1990). Most of the reported studies on chronic patients to date did not define the clinical stability or chronicity of the patients involved. Further, previous studies of patients who were not in a state of acute relapse have also included patients in continuing care (long-stay) wards. Such a population does not necessarily help us in trying to understand depressive symptoms in today's population of patients, most of whom have had very different programmes of care and who have spent most of their ‘career’ in the community. Only one previous study (Pogue-Geile, 1989) described patients who were regarded as clinically stable and were living in the community, and found 9% to be currently depressed. Clinical stability was defined as: not hospitalised in the previous 6 months; no medication changes in the previous 6 weeks; and, judged by their psychiatrist to be stable.

The term ‘post-psychotic depression’ has been used to describe depressive symptoms arising during or after the resolution of a psychotic episode (McGlashan and Carpenter, 1978, Siris et al., 1988). The ICD-10 (World Health Organisation, 1992) definition of ‘post-schizophrenic depression’ avoids the issue of aetiology, describing this as a depressive episode, arising in the aftermath of a schizophrenic illness, with schizophrenic symptoms often still present but no longer dominating the clinical picture.

The first aim of this study is to ascertain the point prevalence of a state of ‘depression’ in otherwise clinically stable chronic schizophrenic patients in the community, using the ICD-10 approach to definition. The second aim is to examine the relationship between the depressive symptoms and other features of the illness, demographic variables and drug treatment. In addition, we sought to examine the extent to which depressive symptoms and negative symptoms overlap and whether use of certain rating scales makes differentiation easier.

Exploring the prevalence and associations of such symptoms in a clinically stable population of patients in the community may help to quantify the contributions made by various factors. We aimed to make our population relatively ‘pure’, so as to remove some of the confounding factors that can be difficult to account for in samples chosen in a less discriminating way. For example, it can be difficult to separate the effects of simply being in hospital from those of acute relapse.