Negative symptoms and not cognition predict social functioning among patients with schizophrenia

Abstract

It is well known that patients with schizophrenia have some degree of cognitive impairment, such as deficits in executive functions. There has been a debate over the influence of cognitive impairment in the outcome of schizophrenia, compared to the influence of positive or negative symptoms. Negative symptoms are more chronic and persistent and less responsive to treatment. They are also associated with poor premorbid adjustment, poor social functioning, greater likelihood of cognitive impairment and brain ventricular enlargement. The aim of this study was to relate psychopathological measures and neurocognitive tests to social outcome, to find out which measure is the best predictor of social outcome in the long run. Forty-nine subjects with a DSM-IV diagnosis of schizophrenia were recruited from inpatient and outpatient units in East Yorkshire, UK. The patients were taking conventional and atypical antipsychotic drugs. Psychopathological measures (Brief Psychiatric Rating Scale [BPRS], total and subscales), neurocognitive tests (the Rivermead Behavioural Memory Test, the Intra/Extra Dimensional Shift Test, the Stockings of Cambridge Test) and social outcome scales (Social Behaviour Scale [SBS] and Independent Living Skills Survey, reduced version) were administered at baseline, 9 months and 18 months. The Social Behaviour Scale was developed by the MRC Social Psychiatry Unit, with chronic institutionalised subjects, whilst the Independent Living Skills Survey was designed to provide an assessment of independent living skills in the community of chronically mentally ill patients living in residential care facilities. A stepwise multivariate regression analysis using psychopathological measures and neurocognitive tests as predictors and social functioning scales as outcome showed that negative symptoms were the strongest predictor of social functioning both at 9 months and 18 months. This is the most important finding of this study. The regression analysis at 9 months, with SBS score as the dependent variable, produced a significant overall model (F = 4.748, p <0.05, with R square = 0.126; adjusted R square = 0.099). The only significant partial contribution was made by the BPRS withdrawal retardation dimension (beta = 0.355; p <0.05). Regression analysis at 18 months with the SBS score as the dependent variable also produced a significant model (F = 9.110, p <0.01, with R square = 0.275; adjusted R square = 0.245) and confirmed that the BPRS withdrawal retardation dimension was the only significant predictor in the model (beta = 0.525, p <0.01). In spite of the limitations of this study (small sample size, use of reduced versions of the Independent Living Skills Survey and use of the withdrawal-retardation dimension of the Brief Psychiatric Rating Scale only as a measure of negative symptoms), these findings point in the direction of the importance of negative symptoms' control in schizophrenia.