Clinical and Sociodemographic Correlates of Serum Unconjugated Bilirubin in Patients with Severe Psychiatric Disorders

Abstract

Background: Serum unconjugated bilirubin (UCB) is studied as a peripheral oxidative-stress marker in severe psychiatric illness, but levels are also shaped by sociodemographic and clinical factors -- age, sex, marital status, tobacco use, family history, illness duration -- that must be characterised first. The present study aimed to characterise clinical and sociodemographic correlates of serum UCB in schizophrenia and bipolar affective disorder (BPAD) versus controls, and determine whether diagnostic UCB differences persist independently of these correlates. Methods: This cross-sectional study at the Institute of Mental Health and Hospital, Agra, enrolled 180 subjects (60 each: schizophrenia, BPAD, controls) via consecutive purposive sampling, with diagnoses per ICD-10 and controls screened using GHQ-12. Fasting UCB (total minus conjugated bilirubin) and sociodemographic/clinical data were recorded via structured proforma. Group differences were tested with one-way ANOVA, Tukey's post-hoc test, and ANCOVA adjusting for age, sex, tobacco use, family history, illness duration; p < 0.05 was significant. Results: Groups were matched for age/sex but differed in marital status, family history, tobacco use, and illness duration. Mean UCB was 0.61 ± 0.32 mg/dL in controls, 0.83 ± 0.36 in BPAD, and 0.93 ± 0.36 in schizophrenia, with elevated UCB in 11.66%, 41.66%, and 61.66%, respectively. ANOVA showed a significant group effect (F = 17.45, p < 0.001) with a schizophrenia > BPAD > controls gradient, significant after ANCOVA adjustment (adjusted F = 15.82, p < 0.001). Conclusion: Serum UCB in schizophrenia and BPAD reflects sociodemographic and clinical correlates, yet its diagnostic gradient persists independently, supporting candidacy as an oxidative-stress biomarker. Tobacco use, family history, and illness duration should be documented and adjusted for when UCB is used as a psychiatric marker.

Keywords: Bipolar affective disorder; clinical correlates; oxidative stress; schizophrenia; sociodemographic correlates; unconjugated bilirubin