Inconclusive Evidence for the Efficacy of Olanzapine in the Treatment of Negative Symptoms in Schizophrenia

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Sir: In a recent systematic review of the pharmacologictreatment of primary negative symptoms in schizophrenia, mycolleagues and I¹ concluded that there was a paucity of evidenceregarding efficacy of treatments of primary negative symptomsand that the lack of standardized research designs had ledto marked inconsistencies in results. A case in point wasolanzapine’s efficacy against primary negative symptoms. Ofthe 4 conducted trials, the only study to use selected patientswith primary negative symptoms found no benefit²; 2 studiesusing path analysis suggested the reverse,^3,4 while a third wasambivalent.⁵‘ ‹