Insulin resistance and increased leptin concentrations in noncompliant schizophrenia patients but not in antipsychotic-naive first-episode schizophrenia patients

Background: The onset of diabetes and impaired glucose metabolism among schizophrenic patients has been the topic of numerous recently published articles, with research implicating weight gain, the use of antipsychotic medication, history of diabetes mellitus in family members, and the diagnosis of schizophrenia itself as risk factors. Therefore, it was the aim of this study to determine the glucose metabolism parameters in noncompliant unmedicated schizophrenic patients (antipsychotic-free) and first-episode antipsychotic-naive schizophrenic patients to investigate whether there is a preexisting impairment of glucose metabolism in never-medicated schizophrenic patients. Method: Plasma glucose, insulin, C-peptide, and leptin concentrations were determined in 50 antipsychotic-free and 50 antipsychotic-naive DSM-IV schizophrenia patients and 50 healthy control subjects. Insulin resistance was calculated through the homeostatic model assessment (HOMA). The General Linear Model (univariate) procedure was used to perform analysis of covaritance. Patients were recruited from July 2001 to December 2002. Results: Antipsychotic-free patients showed significantly increased insulin (p = .001) and C-peptide (p = .02) concentrations and a significantly higher degree of insulin resistance (p = .003), as measured with the HOMA index, in comparison with the antipsychotic-naive patients and the control group. Significantly increased leptin concentrations (p = .000) were also noted in the anti psychotic-free patients and were attributed to the effects of body mass index (p = .000) and sex (p = .000). Conclusions: The results reported in this study suggest the effect of previous antipsychotic treatment on glucose metabolism parameters and weight-related hormones such as leptin, while ruling out a preexisting impairment of glucose metabolism in never-medicated first-episode schizophrenic patients.