A higher body mass index in Chinese inpatients with chronic schizophrenia is associated with elevated plasma orexin-A levels and fewer negative symptoms.

Orexin-A is involved in numerous physiological functions, such as feeding behavior and energy balance. Yet, the associations among the orexin system, weight changes and the clinical symptoms of schizophrenia patients remain uncertain, especially in inpatients with chronic schizophrenia (CS). The purpose of this study was to investigate the relationship between the orexin-A levels, body mass index (BMI) and clinical symptoms of CS inpatients. Altogether, 324 inpatients were enrolled in our study. The clinical symptoms of all inpatients were measured using a 30-item Positive and Negative Syndrome Scale (PANSS), and then we calculated the BMI of each subject and tested the orexin-A levels by ELISA methods. The orexin-A levels of the CS inpatients in the obesity group (1.24±1.45ng/ml, =52) were significantly higher than those in the non-overweight group (0.85±1.18ng/ml, =176) and the overweight group (0.97±1.15ng/ml, =96). Spearman's correlation analysis showed that higher BMIs were associated with higher plasma orexin-A levels and fewer negative symptoms. Furthermore, the multiple regression analysis indicated that the orexin-A level could be a contributor to BMI (=30.21, <0.001). However, there was no correlation between plasma orexin-A concentrations and clinical symptoms in our research. A higher plasma orexin-A level may be a factor influencing the BMI of inpatients with CS, and fewer negative symptoms seem to be correlated with higher BMI, but the causality among BMI, orexin-A and clinical symptoms of schizophrenia requires further clinical research.