A retrospective study on the association between bilirubin levels and weight gain in patients treated with 'pin group' antipsychotics (olanzapine, quetiapine, clozapine)

Antipsychotic medications play a fundamental role in the treatment of various psychiatric disorders in clinical practice. In particular, atypical (second-generation) antipsychotics are known not only for their therapeutic efficacy but also for their propensity to cause significant weight gain and contribute to cardiovascular and metabolic complications. Weight gain associated with these medications negatively affects patient adherence to treatment and increases the risk of serious medical conditions such as hypertension, type 2 diabetes, and metabolic syndrome. Consequently, the metabolic side effects of antipsychotics have gained increasing attention, leading to a growing body of research in this area. The aim of this study is to investigate whether baseline bilirubin levels, which can be assessed through routine blood tests prior to initiating treatment with "pin group" atypical antipsychotics, can predict the risk of weight gain and metabolic syndrome associated with these medications. The sample of our study consists of patients who were hospitalized and treated in the Psychosis Unit of Pamukkale University Psychiatry Hospital between 2013 and 2023. A total of 162 patients who met the inclusion criteria and did not meet any of the exclusion criteria were included in the study. From the hospital records, the following parameters obtained from routine blood tests at the time of admission were recorded and analyzed: AST, ALT, GGT, LDH, ALP, triglycerides, cholesterol, HDL, LDL, fasting blood glucose, total bilirubin, direct bilirubin, and indirect bilirubin. Additionally, weekly body weight measurements of the patients were recorded and examined. In our study, the differences between the initial weight measurements and subsequent weekly measurements in the group receiving olanzapine were found to be statistically significant. In the quetiapine group, except for the difference between the first and last week's weight measurements, the changes in weight across other weeks were also statistically significant. It was observed that weight gain associated with olanzapine, clozapine, and quetiapine was not correlated with the dosage of the medication. In the olanzapine group, patients with lower baseline body weight also had lower fasting blood glucose levels. The disappearance of this correlation during weekly follow-ups as patients gained weight suggests that those with lower fasting glucose levels may be more prone to greater weight gain. The findings of our study are consistent with the existing literature and indicate that baseline fasting glucose levels may be an important predictor of weight changes induced by olanzapine treatment. In our study, a statistically significant positive correlation was found between triglyceride levels and weight gain in the group of patients using olanzapine, compared to those who were not using it. In the quetiapine group, LDL levels were found to be significantly positively correlated with weekly weight gain, whereas HDL levels showed a statistically significant negative correlation. No statistically significant relationship was found between direct bilirubin levels and weight gain in any of the patient groups. Among patients receiving olanzapine, those with lower baseline body weight were found to have higher levels of indirect bilirubin. The disappearance of this correlation over the course of weekly follow-ups, as patients gained weight, suggests that higher baseline indirect bilirubin levels may be associated with greater weight gain compared to those with lower levels. Significant weight gain and metabolic disturbances caused by atypical antipsychotics are major contributors to treatment non-adherence and have been associated with reduced life expectancy in patients with schizophrenia. Therefore, regular monitoring and prevention of weight gain and metabolic abnormalities induced by atypical antipsychotics are of critical importance.