Neurocognitive performance and negative symptoms: are they equal in explaining disability in schizophrenia outpatients?

Objective: The aim of this study is to assess if cognitive variables and symptom dimensions can predict disability in a sample of outpatients with schizophrenia.

Method: A cross-sectional sample of 113 individuals with a diagnosis of schizophrenia (DSM-IV criteria) was selected from a computerized register of five Community Mental Health Centers. Patients were assessed by two trained psychologists, with a neuropsychological battery comprising measures for verbal memory, attention, operative memory and abstraction and flexibility functions. Symptoms were assessed with the Positive and Negative Syndrome Scale (PANSS); a socio-demographic and clinical questionnaire, comprising the Disability Assessment Scale (DAS), was also completed. Test scores were standardized (t scores) to performance of healthy controls. To assess the relationship between clinical and sociodemographic factors and disability and cognitive functioning Pearson's correlation coefficients were computed. In order to establish the predictive capacity of the cognitive, clinical and symptom variables on disability linear regression models were fitted.

Results: Mean age of patients was 41.6 years and 68% were male. Higher ratings in the negative dimension were associated with more cognitive deficits. Association with the positive dimension was present but less strong. All disability areas, except for disability in occupational functioning, were partially explained by the negative dimension. Disability in family functioning was also partially explained by attention and number of admissions since onset.

Conclusion: Negative symptoms are the major source of disability of our sample and are also associated to cognitive functioning. The present findings suggest that further investigation on the mediators between clinical and social outcomes may help to design specific treatments to reduce disability.