The Effect of Synbiotic as an Adjuvant Therapy to Fluoxetine in Moderate Depression: A Randomized Multicenter Trial

Background: Depression is a serious and burdensome disorder in modern societies, with lifetime prevalence of about 16%. Disturbed immune responses in the gut and immune-privileged sites including the central nervous system might occur subsequent to dysbiosis of gut microbiome. In this study we aimed at assessing the efficacy of 6 weeks synbiotic supplementation in the treatment of moderate depression in a double-blind, placebo-controlled, multi-center, and randomized trial. Methods: A total of 40 adult outpatients, who met the diagnostic and statistical manual of mental disorders fifth edition for moderate depression, were recruited based on the structured interview for DSMV. Recruited patients had a Hamilton rating scale for depression (HAM-D) score of 17 to 23 at baseline. All patients received fluoxetine (20 mg/d) for 4 weeks. Then, either a synbiotic capsule (plus fluoxetine) or placebo (plus fluoxetine) was added to the therapy for 6 weeks. Results: The mean age of the participants in the synbiotic treated group was 34.45 years and it was 35.50 years in the placebo group. Following the adjustment of ANCOVA models for gender, age, and BMI at baseline, there was a greater reduction in HAM-D score in synbiotic treated patients (Mean ± SD = -19.25 ± 1.71) compared to placebo taking group (Mean ± SD = -17.75 ± 2.05; P = 0.024). At the end of the 10th week of the intervention and after applying ANCOVA adjusted for the mentioned variables as well as baseline HAM-D score, it was found that the synbiotic group had a significantly decreased HAM-D score compared to the placebo (3.65 vs. 4.80, P = 0.013). Conclusions: The results of the current study revealed the efficacy of synbiotic as an adjuvant therapy in moderate depression.