Background: Mental disorders is one of the main causes of disability and lower life expectancy among patients with Multiple Sclerosis (MS). The present trial aimed to examine the efficacy of multi-strain probiotic supplementation on circulating levels of BDNF, NGF, IL-6 and mental health in patients with MS.

Methods: This trial was conducted among 70 patients with MS that referred to the MS Association. Patients were randomized into intervention and control groups to receive 2 multi-strain probiotic capsules or placebo, daily for six months. Serum BDNF, NGF and IL-6 was measured by ELISA kits. Mental health parameters were assessed by valid questionnaires in the baseline and end of the study.

Results: Of the 70 patients enrolled in this study, 65 subjects were included in the final analysis. From baseline to 6 months, probiotic supplementation resulted in a significant increase in BDNF and a significant reduction in the IL-6 levels (P < 0.001). Our findings revealed that probiotic supplementation compared to placebo caused a significant improvement in the general health questionnaire-28 (GHQ-28) (-5.31 ± 4.62 vs. -1.81 ± 4.23; P = 0.002), Beck Depression Inventory-II (BDI-II) (-4.81 ± 0.79 vs. -1.90 ± 0.96; P = 0.001), Fatigue Severity Scale (FSS) (-3.81 ± 6.56 vs. 0.24 ± 5.44; P = 0.007) and Pain Rating Index (PRI) (-3.15 ± 4.51 vs. -0.09 ± 3.67; P = 0.004). However, we not found any significant difference between the two groups in other factors (P > 0.05).

Conclusion: Overall, six months of probiotic supplementation resulted in greater improvement in mental health parameters.