A determinant of insulin resistance in patients with schizophrenia

Background/Aims: As compared with the general population, patients with schizophrenia have a higher risk of obesity and glucose metabolism impairment. Moreover, some antipsychotic drugs add to this risk owing to side effects such as weight gain. However, few reports exist regarding the pathophysiology of insulin resistance in drug-naive or drug-free schizophrenic patients. Therefore, the aim of the present study was to investigate the factors that contribute to insulin resistance in antipsychotic drug-naive and drug-free schizophrenic patients. Methods: Nineteen (4 men, 15 women) drug-naive or drug-free subjects with schizophrenia and nineteen age- and sex-matched controls were recruited for participation in this study. We measured weight, height, waist circumference, biochemical profiles, body fat percentage, and calculated body mass indices (BMI) in all patients. Furthermore, we correlated HOMA-IR, a marker for insulin resistance, with anthropometric measures and clinical characteristics. Results: There were no significant differences in BMI, waist circumference, or body fat percentage between the two groups. In addition, there were no differences in blood pressure, glucose, HbA1c, insulin, HOMA-IR, total cholesterol, HDL-cholesterol, or LDL-cholesterol; however, triglyceride levels and 24 hr urine free cortisol levels were higher in schizophrenic patients. There was also a significant correlation between HOMA-IR and both age and waist circumference in the control group. Additionally, HOMA-IR was significantly correlated with 24 hr urine free cortisol levels in schizophrenic patients. Conclusions: The study shows that risk factors for insulin resistance in drug-naive or drug-free schizophrenic patients do not differ from those of the control group; however, the major determinant of insulin resistance in schizophrenia patients was that of increased cortisol levelsope