Research has identified distinct trajectories of antipsychotic response in patients with chronic schizophrenia in short-duration trials (~12 weeks). This post-hoc analysis identified trajectories in patients with chronic schizophrenia treated for ≤24 weeks. We pooled data from 1990 patients with chronic schizophrenia from 6 randomized, double-blind, olanzapine-comparator trials of atypical antipsychotics. Trajectory analysis identified homogeneous subpopulations within the larger heterogeneous population. Baseline demographics were compared between the identified latent classes. Five distinct response trajectories based on Positive and Negative Syndrome Scale (PANSS) Total score were identified: Dramatic Responders (n=47/1990, 2.4%), severely-ill patients (PANSS=124) with rapid and sustained improvement (51%) by Week 3; Partial Responders (n=1802/1990, 90.6%), moderately-ill (PANSS=90) with minimal improvement (21%) by Week 4, and little further improvement; Partial Responders-Unsustained (Late) (n=32/1990, 1.6%), markedly-ill (PANSS=95) with minimal initial improvement followed by worsening after Week 12; Partial Responders-Unsustained (Early) (n=28/1990, 1.4%), markedly-ill (PANSS=102) with minimal initial improvement followed by worsening after Week 8; and Delayed Responders (n=81/1990, 4.1%), markedly-to-severely-ill (PANSS=113) with minimal (11%) improvement at Week 8, but noticeable improvement thereafter (49%). Significant differences were noted for several baseline characteristics (p<.05) and discontinuation rates (46%-72%). Dramatic Responders were younger and more likely to be female and Hispanic with higher baseline illness severity. Analysis of antipsychotic response over 24 weeks in a large, pooled, heterogeneous population treated for schizophrenia revealed 5 distinct trajectories. Most patients had modest and sustained improvements during atypical antipsychotic treatment, regardless of their baseline illness severity, representing a partial response to currently available treatments.
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