The aim of this study is to measure GABA levels of perisylvian cortices in schizophrenia and bipolar disorder patients, using proton magnetic resonance spectroscopy (1H-MRS). Patients with schizophrenia (n=25), bipolar I disorder (BD-I; n=28) and bipolar II disorder (BD-II; n=20) were compared with healthy controls (n=30). 1H-MRS data was acquired using a Siemens 3T whole body scanner to quantify right and left perisylvian structures' (including superior temporal lobes) GABA levels. Right perisylvian GABA values differed significantly between groups [chi2=9.62, df: 3, p=0.022]. GABA levels were significantly higher in the schizophrenia group compared with the healthy control group (p=0.002). Furthermore, Chlorpromazine equivalent doses of antipsychotics correlated with right hemisphere GABA levels (r2=0.68, p=0.006, n=33). GABA levels are elevated in the right hemisphere in patients with schizophrenia in comparison to bipolar disorder and healthy controls. The balance between excitatory and inhibitory controls over the cortical circuits may have direct relationship with GABAergic functions in auditory cortices. In addition, GABA levels may be altered by brain regions of interest, psychotropic medications, and clinical stage in schizophrenia and bipolar disorder.

OBJECTIVE: This study examined the effect of adjunctive intranasal insulin therapy on psychopathology and cognition in patients with schizophrenia. METHODS: Each 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. RESULTS: A 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). CONCLUSIONS: Adjunctive 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.