Diagnostic and Predictive Utility of Plasma Phosphoethanolamine Levels in Depressive Disorder: A Naturalistic Observational Study.

OBJECTIVES: Plasma phosphoethanolamine (PEA) has been proposed as a potential biomarker for depressive disorder. To further assess its diagnostic utility and relevance across psychiatric conditions, we conducted a larger observational study in a psychiatric primary care setting. METHODS: Between 2013 and 2020, 576 patients underwent DSM-5-based psychiatric assessments. Plasma PEA levels were measured in 295 patients with depressive disorders, 264 with other psychiatric disorders, and 17 with physical illnesses. RESULTS: PEA demonstrated moderate or high diagnostic accuracy for depressive disorder (AUC = 0.81, 95% CI: 0.78-0.85). Lower PEA levels were significantly associated with depression (OR = 16.30, p < 0.001). CONCLUSIONS: These findings suggest that plasma PEA concentration may serve as a useful biomarker for depressive disorder. Further studies are warranted to explore its potential relationship with white matter pathology in psychiatric conditions.