Probiotic supplementation → Depression
Higher Probiotic supplementation decreases Depression.
Kazemi 2020 found that eight weeks of Lactobacillus helveticus and Bifidobacterium longum lowered the Beck Depression Inventory from 17.39 to 9.1 versus 18.18 to 15.55 on placebo in 81 completers with major depression. Akkasheh 2016 saw a similar Beck drop in 40 people.
Randomized trial · Contested · N=81
Supported by an experiment or a tightly identified design. Read the caveats.
Mechanism
Authors treat named gut strains as a way to change mood. They do not isolate one metabolite. Kazemi, Noorbala, Azam, Eskandari and Djafarian assigned 110 people with major depression to probiotic, prebiotic, or placebo for eight weeks. 81 finished. Beck scores fell from 17.39 to 9.1 on probiotic versus 18.18 to 15.55 on placebo (P=0.042). The prebiotic arm did not beat placebo. Akkasheh, Kashani-Poor, Tajabadi-Ebrahimi and colleagues assigned 40 people with major depression to a three-strain capsule (L. acidophilus, L. casei, B. bifidum) or placebo for eight weeks. Beck scores moved -5.7 versus -1.5 (P=0.001). Insulin, HOMA-IR, and hs-CRP also fell. Sempach, Doll, Limbach and colleagues re-analyzed 43 people from a four-week probiotic-plus-usual-care trial (19 probiotic, 24 placebo). This file is immune and ghrelin. The abstract names a depression drop from the same assignment.
Caveats
Researchers assigned people to a capsule or a control, so this is a trial stamp. Strains and durations differ. More papers of the same design do not settle the claim. Kazemi is 81 completers and a Beck score. Akkasheh is 40 people. Sempach is a secondary immune file; the depression claim sits in the parent sentence. This is a journal entry, not medical advice and not a reason to take a probiotic for depression.
Effect
qualitative. Kazemi 2020: L. helveticus+B. longum, 8 wk, 81/110 MDD, BDI 17.39 to 9.1 vs 18.18 to 15.55. Akkasheh 2016: N=40, BDI -5.7 vs -1.5. Sempach 2024: N=43, 4 wk, secondary.
Nodes
Named confounders
Cite this page
What Causes What. “Probiotic supplementation → Depression.” https://whatcauseswhat.org/edges/e-probiotic-depression (atlas updated 2026-09-02).
Papers
- Effect of probiotic and prebiotic vs placebo on psychological outcomes in patients with major depressive disorder: A randomized clinical trial.
A Kazemi, AA Noorbala, K Azam, MH Eskandari, K Djafarian · 2020 · Clinical nutrition (Edinburgh, Scotland)
- Clinical and metabolic response to probiotic administration in patients with major depressive disorder: A randomized, double-blind, placebo-controlled trial.
G Akkasheh, Z Kashani-Poor, M Tajabadi-Ebrahimi, P Jafari, H Akbari, M Taghizadeh, MR Memarzadeh, Z Asemi · 2016 · Nutrition (Burbank, Los Angeles County, Calif.)
- Examining immune-inflammatory mechanisms of probiotic supplementation in depression: secondary findings from a randomized clinical trial.
L Sempach, JPK Doll, V Limbach, F Marzetta, AC Schaub, E Schneider, C Kettelhack, L Mählmann · 2024 · Translational psychiatry