Background. The effectiveness of therapeutic interventions in psychosis is increasingly reported in terms of reductions in different symptom dimensions. It remains unclear, however, to what degree such symptomatic changes are accompanied by improvement in other measures such as service use, quality of life, and needs for care.

Methods. A sample of 708 patients with chronic psychotic illness was assessed on three occasions over 2 years (baseline, year 1 and year 2). A multilevel analysis was conducted to examine to what degree reduction in psychopathological scores derived from factor analysis of the Comprehensive Psychopathological Rating Scale (CPRS), was associated with improvement in service use, disability, subjective outcomes and measures of self-harm.

Results. Reduction in positive, negative, depressive and manic symptoms over the study period were all independently associated with lessening of social disability. Reduction in negative symptoms, and to a lesser extent in positive and manic symptoms, was associated with less time in hospital and more time living independently, whereas changes in positive and manic symptoms resulted in fewer admissions. Subjective outcomes such as improvement in quality of life, perceived needs for care and dissatisfaction with services showed the strongest associations with reduction in depressive symptoms. Reduction in positive symptoms was associated with decreased likelihood of parasuicide. Results did not differ according to diagnostic category.

Conclusion. The findings suggest that changes in distinct psychopathological dimensions independently and differentially influence outcome. Therapeutic interventions aimed at reducing symptoms of more than one dimension are likely to have more widespread effects.