OBJECTIVEThis study examined the effect of adjunctive intranasal insulin therapy on psychopathology and cognition in patients with schizophrenia.METHODSEach subject had a Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, diagnosis of schizophrenia or schizoaffective disorder and been on stable antipsychotics for at least 1 month. In an 8-week randomized, double-blind, placebo-controlled study, subjects received either intranasal insulin (40 IU 4 times per day) or placebo. Psychopathology was assessed using the Positive and Negative Syndrome Scale and the Scale for Assessment of Negative Symptoms. A neuropsychological battery was used to assess cognitive performance. The assessment for psychopathology and cognition was conducted at baseline, week 4, and week 8.RESULTSA total of 45 subjects were enrolled in the study (21 in the insulin group and 24 in the placebo group). The mixed model analysis showed that there were no significant differences between the 2 groups at week 8 on various psychopathology and cognitive measures (P > 0.1).CONCLUSIONSAdjunctive therapy with intranasal insulin did not seem to be beneficial in improving schizophrenia symptoms or cognition in the present study. The implications for future studies were discussed.