RESUMEN
OBJECTIVE: This study compared saliva levels of 3-methoxy-4-hydroxyphenylglycol (sMHPG) in patients with major depressive disorder (MDD) to levels in healthy controls and explored whether sMHPG levels in patients with MDD were a predictive marker for antidepressant efficacy. METHODS: sMHPG levels were compared in 53 patients with MDD and 275 age-matched healthy controls. Patients' depressive symptoms were assessed by the 17-item Hamilton Rating Scale for Depression at baseline and 4 weeks after treatment with selective serotonin reuptake inhibitors (SSRIs, n = 23) or mirtazapine (n = 30), followed by saliva sampling. The mirtazapine group included nine patients who had been treated with an SSRI for more than 4 weeks without any improvement. sMHPG levels were measured by gas chromatography-mass spectrometry. RESULTS: sMHPG levels in MDD patients were significantly higher than in controls. The responder rate to drug treatment at 4 weeks was 62% for mirtazapine (13/21), 57% for SSRIs (13/23), and 89% (8/9) for SSRI plus mirtazapine. sMHPG at baseline in 13 responders treated with SSRIs, but not mirtazapine, was significantly higher than that in non-responder group and showed consequent reduction 4 weeks after treatment. The area under the receiver operating characteristic (ROC) curves of sMHPG for discrimination of SSRI responders and non-responders was 0.86 ± 0.10 (95% confidence interval: 0.64-1.0, p = 0.005). In contrast, the ROC curve of sMHPG levels for discrimination of mirtazapine responders and non-responders was not significant. Adjunctive treatment with mirtazapine to SSRI non-responders was effective, regardless of baseline sMHPG levels. CONCLUSION: sMHPG in patients with MDD was higher than in healthy controls. High baseline sMHPG levels in patients with MDD maybe a predictive marker for SSRI response.