“Probiotics improve mood and anxiety.”
Probiotics have only a small average effect on mood and anxiety, much smaller than the gut-brain hype suggests.
A probiotic is not a proven fix for low mood or anxiety. For people with depression, trials show a modest added benefit that varies a lot between products and studies, so a probiotic is an optional extra, not a replacement for therapy or medication.
If you want to try one, choose a product that names its strain and dose, use it for a few weeks while noting your mood, and stop if nothing changes.
Safety note: Probiotics are generally safe for healthy people, with mild gas or bloating at most. Rare serious infections have occurred in people who are very ill, have a weakened immune system or a central IV line, and in premature babies.
Talk to a healthcare professional if: you have a weakened immune system, a serious illness or a central IV line and want to take a probiotic, or low mood or anxiety lasts or makes daily life hard. If you have thoughts of harming yourself, get help right away.
Pooled trials point to a real but small average benefit, mostly in people who already have depression or another medical condition. Confidence is limited because trials test many different strains and doses, most are small, and results vary so widely that the larger pooled numbers are hard to trust.
Probiotics have only a small average effect on mood and anxiety, much smaller than the gut-brain hype suggests. In a review of 34 controlled trials, probiotics lowered depression scores slightly and anxiety scores very slightly, with a larger effect in people with depression or other medical conditions than in healthy people.
A probiotic is a specific live strain at a specific dose, so results for one product do not carry over to another. In an earlier review of 10 trials, mostly in healthy people, probiotics made no clear difference to mood overall. A 2025 review of 19 studies in people with depression reported large drops in symptoms, but results differed so much between studies that the pooled number is hard to trust. Prebiotics, the fibers that feed gut bacteria, showed no effect on depression or anxiety in the 34-trial review.
- Liu RT, Walsh RFL, Sheehan AE. Prebiotics and probiotics for depression and anxiety: A systematic review and meta-analysis of controlled clinical trials. Neuroscience and Biobehavioral Reviews. 2019;102:13-23. DOI: 10.1016/j.neubiorev.2019.03.023. PMID: 31004628. PMCID: PMC6584030
- Ng QX, Peters C, Ho CYX, Lim DY, Yeo WS. A meta-analysis of the use of probiotics to alleviate depressive symptoms. Journal of Affective Disorders. 2018;228:13-19. DOI: 10.1016/j.jad.2017.11.063. PMID: 29197739
- Moshfeghinia R, Nemati H, Ebrahimi A, Shekouh D, Karami S, Eraghi MM, Mohagheghzadeh H, Hunter J, Pasalar M. The impact of probiotics, prebiotics, and synbiotics on depression and anxiety symptoms of patients with depression: A systematic review and meta-analysis. Journal of Psychiatric Research. 2025;188:104-116. DOI: 10.1016/j.jpsychires.2025.05.053. PMID: 40440772
- National Center for Complementary and Integrative Health. Probiotics: Usefulness and Safety. Updated 2025