Association between changes on the Negative Symptom Assessment scale (NSA-16) and measures of functional outcome in schizophrenia

We examined whether changes in negative symptoms, as measured by scores on the 16-item Negative Symptom Assessment scale (NSA-16), were associated with changes in functional outcome. A group of 125 stable outpatients with schizophrenia were assessed at baseline and at 6 months using the NSA-16, the Brief Psychiatric Rating Scale, and multiple measures of functional outcome. Baseline adjusted regression coefficients indicated moderate correlations between negative symptoms and functional outcomes when baseline values of both variables were controlled. Results were nearly identical when we controlled for positive symptoms. Cross-lag panel correlations and Structural Equation Modeling were used to examine whether changes in negative symptoms drove changes in functional outcomes over time. Results indicated that negative symptoms drove the changes in the Social and Occupational Functioning Scale (SOFAS) rather than the reverse. Measures of Quality of Life and measures of negative symptoms may be assessing overlapping constructs or changes in both may be driven by a third variable. Negative symptoms were unrelated over time to scores on a performance-based measure of functional capacity. This study indicates that the relationship between negative symptom change and the change in functional outcomes is complex, and points to potential issues in selection of assessments.