Prognostic value of melatonin in the treatment of major depressive disorder

Introduction: In our study we aimed to determine the correlation between plasma melatonin (MLT) level after 48 hours of anitdepressant treatment and the response at the 8th week of antidepressant treatment and the change in cognitive functions in patients diagnosed with Major Depressive Disorder (MDD). Method: Our study was planned as a cross-sectional prospective paired case-control study. Between January 2021-January 2022 50 participants diagnosed with Major Depressive Disorder according to DSM-5 criteria and anmitted to the Psychiatry Outpatient Clinic of Bezmialem Vakıf University Medical Faculty Hospital and 50 healthy controls were included in the study. Hamilton Depression Rating Scale (HDRS), Hamilton Anxiety Rating Scales (HADS), Pittsburgh Sleep Quality Scale (PUKI) and Wisconsin Card Matching Test (WCST) were administered to all participants in the study. The clinical interviews, scales and neurocognitive test were applied and then blood was drawn to measure melatonin levels. The plasma MLT level was measured 48 hours after the antidepressant treatment and the relationship with the response at 8th week of the antidepressant treatment and the change in executive functions was evaluated. Results: In our study at 8th week of antidepressant treatment there was a significant decrease in HRDS scores in both 20mg group and 40mg group (p=0.001; p=0.002). However, at 8th week of antidepressant treatment only the patients from the 20mg group had a significant decrease in their PUKI scores (p=0.006), similarly, a significant decrease/increase in WCST parameters was found in the patients from the 20mg group (p<0.05). Unlike of most studies results, the morning MLT level was found to be significantly higher in the untreated patient group compared to the healthy controls (p=0.001). Pre-treatment MLT level was found to be significantly lower in patients from the 40mg group compared to the patients from the 20mg group (p<0.05). A similar difference was found in 48 hours MLT levels, both the patients from 20mg group and patients from the 40mg group show significantly increase of MLT in 48 hours, but this increase was higher in the 20mg group (p=0.004). Conclusion: We think that these findings obtained from our study may predict the response to antidepressant treatment with an increase in MLT level in the blood. The findings of our study show that MLT can be an important biochemical marker in terms of its usability in the follow-up and treatment of patients diagnosed with MDD. Keywords: Majör Depresif Disorder, melatonin, executive functions, fluoxetine.