BDNF and major depressive disorder: In MS studies, positive benefits of different probiotic combinations include improvement in clinical scores such as the Expanded Disability Status Scale (EDSS), Beck Depression Inventory (BDI)-II, and General Health Questionnaire (GHQ), and mental health, correlating with modulation of brain-derived neurotrophic factor (BDNF), IL-6, suppression of IL-17 CD4 + T cells, enhanced Tregs and regulatory B cells (Bregs) and expression of IL-10 (Kouchaki et al., 2017; Salami et al., 2019; Mestre et al., 2020; Jiang et al., 2021; Rahimlou et al., 2022).