Treatment response heterogeneity in the predominant negative symptoms of schizophrenia: Analysis of amisulpride vs placebo in three clinical trials

Background: The extent of heterogeneity in response to the psychopharmacological treatment of negative symptoms is unknown. Aims: To examine the extent of heterogeneity in response to the treatment of predominantly negative symptoms of schizophrenia. Method: Data were analyzed from three clinical trials that compared placebo or amisulpride for up to 60. days. Trial participants had predominantly negative symptoms of schizophrenia (n = 485). Heterogeneity of percentage reduction on the Scale for the Assessment of Negative Symptoms (SANS) was examined with trajectory-group based modeling followed by descriptive statistics and the prediction of trajectory group membership with logistic regression modeling. Analyses were repeated separately for the placebo and amisulpride groups. Results: Trajectory group-based modeling identified groups of non- (n = 297, 61.2%), gradual-moderate (n = 135, 27.8%) and rapid- (n = 53, 10.9%) responders. At baseline compared to non-responders, rapid-responders had consistently significantly (p < .05) higher SANS total and subscale scores. Percent SANS improvement at endpoint was greatest for the rapid-responders group, a finding that replicated stratifying by placebo and amisulpride treatment groups. Similarly, in the total sample and stratifying by placebo and amisulpride groups, dropout was not significantly associated with trajectory group membership. Conclusions: Trajectories of treatment response to the psychopharmacological medication of the negative symptoms of schizophrenia demonstrate substantial heterogeneity. Approximately half of the patients included in our analysis showed little improvement, and the most severely ill at baseline responded the most.