Dysregulation of Serum Serotonin–Melatonin Biosynthetic Pathway Markers in Patients with Obsessive-Compulsive Disorder: A Case-Control Study
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Objective: Obsessive-compulsive disorder (OCD) is a disabling neuropsychiatric disorder associated with disturbances in neurotransmitter systems. This study aimed to investigate serum levels of serotonin, melatonin, and selected enzymes involved in their biosynthetic pathway in patients with OCD, and to determine the correlations among these biochemical markers.
Methods and Materials: This case-control study included 50 patients with OCD diagnosed according to DSM-5 criteria and 15 age- and sex-matched healthy controls. Fasting venous blood samples were collected between 8:00 and 10:00 AM under controlled conditions. Serum concentrations of serotonin, melatonin, tryptophan hydroxylase-1 (TPH-1), aromatic amino acid decarboxylase (AADC), arylalkylamine N-acetyltransferase (AANAT), and acetylserotonin O-methyltransferase (ASMT) were measured using sandwich enzyme-linked immunosorbent assay (ELISA). Statistical analyses were conducted using SPSS version 26, with significance set at p < 0.05.
Findings: Serum levels of serotonin, melatonin, TPH-1, AANAT, and ASMT were significantly lower in patients with OCD than in healthy controls (all p < 0.001). AADC levels were also significantly reduced in the OCD group (p < 0.05). Furthermore, correlation analysis revealed significant positive associations among the studied biochemical parameters in patients with OCD, suggesting coordinated dysregulation within the serotonin–melatonin biosynthetic pathway.
Conclusion: Patients with OCD demonstrated significant reductions in serotonin, melatonin, and related biosynthetic enzymes. These findings support the possible involvement of altered serotonin–melatonin pathway activity in the pathophysiology of OCD and may provide a basis for future biomarker-oriented studies.
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