- This study analyzed the effect of olanzapine on a psychopathology-based scale assessing abnormal thought processes and examined the relationship between improvement on this scale and mania and depression improvement in acutely manic patients.The study sample (N = 254) was pooled from two double-blind, randomized, placebo-controlled clinical trials. Disturbance in thought processes was measured by the Positive and Negative Symptom Scale cognitive component (PANSS-Cognitive) score. Mood severity was measured by the Young-Mania Rating Scale (Y-MRS) and Hamilton Depression Inventory (HAM-D). Last-observation-carried-forward (LOCF) changes from baseline to endpoint (Week 3) were presented for patients who had at least one post-baseline assessment.Olanzapine-treated patients experienced modest but significant improvement in PANSS-Cognitive score (olanzapine: -4.25 n = 124; placebo: -1.69 n = 120, p < 01), regardless of age, gender, mania subtype (pure, mixed), course (rapid or non-rapid cycling), or the presence or absence of psychotic features. PANSS-Cognitive improvement was more highly correlated with mania than depression improvement.Olanzapine improved abnormal thought processes measured by the PANSS-Cognitive score in patients with acute mania. This improvement in thought processes was significantly associated with improvement in acute mania. More sensitive and specific neuropsychological testing could help clarify whether improvement in thought processes on olanzapine was independent of mania reduction.