Longitudinal progression of negative symptoms in schizophrenia: A new look at an old problem

ObjectiveLongitudinal analysis is crucial in determining the ability of new interventions to successfully reduce negative symptoms in schizophrenia. However, there are still conflicting reports as to whether there are significant treatment effects on these symptoms and the extent of these effects. We examine the possible effects of analysis method on these questions.MethodsWe use generalized linear mixed models (GLMM) to assess the change in specific negative symptom items following treatment changes in two separate cohorts of schizophrenia patients, one chronic and one first episode.ResultsBoth data sets indicate that examining the change in prevalence of moderate to severe symptoms provides a useful estimate of the effect size associated with changes in treatment that often differs from that given using analysis of means.ConclusionsThe use of categorical longitudinal methods may be critical to determining the responsiveness of negative symptoms to treatment as well as determining the stability of these symptoms over time.