Time required for initial improvement during clozapine treatment of refractory schizophrenia

Objective: To characterize better the length of time required for the onset of improvement during clozapine treatment for refractory schizophrenia, the author reanalyzed data from a naturalistic outcome study. Method: Medical records of 100 adults sequentially treated with clozapine in a state hospital were reviewed through 18 months. A priori criteria were used to categorize change in a measure of global social functioning. Results: Of 73 patients who met the criteria for at least some improvement during clozapine treatment, 55 demonstrated initial improvement within 6 months, and the remainder demonstrated improvement by month 11. Response at 3 months was significantly correlated with outcome at 18 months. Conclusions: Gross social improvement as measured in this study is likely to lag behind more sensitive indicators of clinical response. This study supports the notion that initial response to clozapine occurs within the first few months of treatment.