Negative symptoms have greater impact on functioning than positive symptoms in schizophrenia: analysis of CATIE data

Increased attention has been given to treatment of negative symptoms and its potential impact on functional outcomes, however previous inferences have been confounded by the fact that measures of functional outcomes often use items similar to those of negative symptoms. We attempted to discern the relative effects of negative symptoms on functioning, as compared to other symptoms, using data from the National Institute of Mental Health CATIE trial of chronic schizophrenia (n=1447) by examining correlations of Positive and Negative Syndrome Scale factors, Calgary Depression Rating Scale and select items from Heinrich's and Lehman's Quality of Life Scales measuring aspects of functioning that did not overlap with negative symptoms. Baseline functioning and change in functioning were more strongly related to PANSS negative factor than any of the other symptoms - though the amount of variance explained by symptom changes in general was small. The data suggests that improvement in negative symptoms may have a distinctive and independent effect on functional outcome relative to other symptoms. This should be further tested in studies where negative symptoms improve without concomitant improvement of other symptoms.