Comparing Serum Zinc and Cortisol Concentrations in Patients with Major Depressive Disorder Treated with Fluoxetine and Cognitive-Behavioral Therapy: A Randomized Clinical Trial

Background and Major depressive disorder (MDD) is a massive challenge for community mental health. Serum zinc and cortisol are suitable biomarkers for assessing the response to a given treatment. In the present study, serum concentrations of these markers were compared between two groups of patients treated with fluoxetine and cognitive behavioral therapy.
In this randomized clinical trial study, 40 female MDD (DSM-V criteria) patients were divided into two groups: fluoxetine therapy (20 mg/daily/3 months, n=20) and group CBT (90-min/once a week/12 weeks, n=20). Severity of depression was studied by Beck Depression Inventory (BDI-II) and serum cortisol and zinc concentrations were measured before and after treatments. Data were analyzed in Graphpad Prism 9.
BDI-II scores significantly reduced in both fluoxetine therapy (from 23.2±1.5 to
11.1± 1.1) and CBT (from 26.8±0.6 to 9.5±0.8) groups after treatments. Serum cortisol level did not change in patients treated with fluoxetine, but it decreased in CBT group (from 453 ± 0.09 to 386.4±0.07). Serum zinc level decreased in the fluoxetine group (from 91.6±4.8 to 72.8±2.8) and increased in the CBT group (from 78.9±2.1 to 86.5±2.6). Post intervention inter-group comparison showed greater decrease in BDI-II score and cortisol concentration in CBT group than the fluoxetine therapy group.
The decrease in BDI-II score and cortisol level and increase in serum zinc were higher in CBT group than fluoxetine group. Therefore, CBT seems to be suitable for treatment of MDD. Further studies are needed with larger sample size and longer study periods.

(Clinical Trials Registry Number: IRCT20190710044171N1)