There is an old saying that you should trust your gut. People have talked about gut feelings, butterflies in the stomach and having the stomach for a fight for as long as anyone can remember, long before anyone could explain why.
In 2013, a group of researchers in Cork, Ireland gave a name to one small part of that old wisdom. They called it psychobiotics, and the word has been quietly growing in popularity ever since.
So what are psychobiotics, and is there any real science behind the idea that the bacteria in your gut might affect your mood? This post covers where the term came from, which strains have actually been studied, and why your dinner plate may matter just as much as any capsule.
Where did the word psychobiotic come from?
The term was coined by Professor Ted Dinan, Professor Catherine Stanton and Professor John Cryan at University College Cork. Writing in the journal Biological Psychiatry in 2013, they described a psychobiotic as "a live organism that, when ingested in adequate amounts, produces a health benefit in patients suffering from psychiatric illness"1.
In a 2016 paper, the same group suggested that prebiotics, the fibres that feed our gut bacteria, could also count as psychobiotics if they influence the conversation between the gut and the brain2.
We will not retell that whole conversation here. If you would like the background first, our guide to the gut brain axis and how digestion affects mood explains how the two are connected.
So, what are psychobiotics in plain English?
Put simply, psychobiotics are live bacteria, or the fibres that feed them, that researchers are studying for their possible effects on mood, stress and the mind. The key word is studying, because this is still a young field.
Our post on probiotics, prebiotics and postbiotics walks through each one.
Why does the strain matter so much?
Bacteria are a little like apples, as two varieties can behave very differently.
Every strain has a full name made up of a genus, a species and a strain code, such as Bifidobacterium longum 1714. The research on psychobiotic strains tends to apply to that exact strain, not to every bacterium that shares its family name.
So when you read about probiotics and mood, look for which strain was actually tested.
Which psychobiotic strains have been studied for stress?
A handful of strains have been looked at more closely than others. Here are three that come up again and again.
Bifidobacterium longum 1714, the Cork strain
In a small 2016 study from the Cork group, 22 healthy volunteers took this strain and were then asked to hold a hand in icy water, a standard lab test for stress. Researchers observed a smaller rise in anxiety and in the stress hormone cortisol, along with lower reported daily stress and subtle changes in memory3.
With only 22 people, this was an early signal rather than a firm answer.
Lactobacillus plantarum PS128, the sleep study strain
In a 30 day pilot study, 40 people living with insomnia took this strain. Researchers reported lower scores for depressive symptoms and fatigue over the month4.
Lactobacillus helveticus R0052 with Bifidobacterium longum R0175
This pairing appears often in the research. A 2025 review of 45 studies found that, when used alongside usual care, it improved scores on a standard depression questionnaire in some trials5.
The same review noted that the studies varied a great deal in their methods, strains and doses5. That makes it hard to draw neat conclusions.
What does the research say about psychobiotics for anxiety and low mood?
The most talked about recent trial came from King's College London in 2023. Published in JAMA Psychiatry, it followed 49 adults with depression who took either a 14 strain mixture or a placebo for eight weeks, alongside their usual antidepressants6.
Those taking the live bacteria showed greater improvements in depression and anxiety scores than the placebo group6. The researchers described it as a pilot, and the study was part funded by the company that made the product, so the results need repeating independently.
Looking at the bigger picture, a 2026 umbrella review gathered the findings of many earlier reviews. It found modest effects on depression that were more consistent than the effects on anxiety7.
There is a catch, though. That same umbrella review judged 76.6% of the reviews it examined to be of moderate, low or critically low quality7.
Do psychobiotics actually work?
The fairest answer is that some specific strains have shown promising early results in small studies, and the effects seen so far tend to be modest. Psychobiotics for anxiety in particular have less consistent evidence than many headlines suggest.
Psychobiotics are a fascinating area of research, not a replacement for proper care.
If you take medication for anxiety or depression, do not stop or change it without speaking to your GP. In the King's College study, the live bacteria were taken alongside medication, never instead of it6.
Can food be a psychobiotic?
This is where everyday life comes in. In a study published in Molecular Psychiatry, the Cork team asked adults to follow a psychobiotic diet for four weeks8.
The diet included six to eight daily servings of fruit and vegetables rich in prebiotic fibre, such as onions, leeks, cabbage, apples, bananas and oats, along with grains, legumes, and two to three servings a day of fermented foods such as sauerkraut, kefir and kombucha8.
People following the diet reported lower perceived stress, and those who stuck to it most closely saw the biggest drops8. The changes to their gut bacteria were only subtle.
Bringing the psychobiotic diet into your kitchen
A bowl of porridge with a sliced banana, a spoonful of sauerkraut beside your lunch, or a pan of leeks and lentils in the evening all fit the pattern.
If fibre is hard to fit into a busy week, our Psyllium Husk Capsules are a simple source of soluble fibre to sit alongside a varied diet. For a more structured starting point, our Gut Health Protocol brings a herbalist's approach to everyday digestive care.
If you would like live bacteria and the fibres that feed them together, our Phytologic Happy Gut Capsules combine named friendly strains with inulin and FOS. They are a food supplement for everyday gut care, not a treatment for low mood.
Mood is shaped by many things, so you may also enjoy our posts on saffron and mental health and adaptogens such as ashwagandha and rhodiola.
When should you talk to someone about your mood?
If you are struggling with your mood, anxiety or sleep, the most important step is to talk to someone. Your GP is a good first port of call, and a pharmacist can check whether anything new suits your current medication.
If you have a weakened immune system or a serious illness, do not start a live bacteria supplement without speaking to your doctor first.
You are also welcome to book a free 15 minute consultation with one of our herbalists.
Frequently asked questions
What are psychobiotics?
Psychobiotics are live bacteria, or the prebiotic fibres that feed them, that are being researched for possible effects on mood and stress. The term was coined by researchers at University College Cork in 20131.
Do psychobiotics actually work?
Some specific strains have shown modest results in small studies, mainly for low mood. Many reviews in this area are of limited quality, so the evidence is still early7.
Which probiotic strain has been studied for stress?
Bifidobacterium longum 1714 is one of the best known. In a study of 22 healthy volunteers, it was linked to a smaller rise in anxiety and cortisol during a stress test3.
Can food be a psychobiotic?
Research suggests food may play a part. A four week psychobiotic diet rich in prebiotic fibre and fermented foods was linked to lower perceived stress8.
Are psychobiotics good for anxiety?
The evidence for anxiety is less consistent than for low mood. A 2026 umbrella review found the effects on depression were more reliable than those on anxiety7.
Can I take live bacteria alongside antidepressants?
Some studies have tested this, but always check with your GP or pharmacist first. Never stop or change prescribed medication without medical advice.
Is a psychobiotic the same as a probiotic?
Not quite. A psychobiotic describes live bacteria or fibres studied specifically for effects on the mind, while the wider group of live bacteria is studied for many different areas of health2.
References
- Dinan, T.G., Stanton, C. and Cryan, J.F. (2013). Psychobiotics: a novel class of psychotropic. Biological Psychiatry. research.ucc.ie.
- Sarkar, A. et al. (2016). Psychobiotics and the manipulation of bacteria gut brain signals. Trends in Neurosciences. research.ucc.ie.
- Allen, A.P. et al. (2016). Bifidobacterium longum 1714 as a translational psychobiotic: modulation of stress, electrophysiology and neurocognition in healthy volunteers. Translational Psychiatry. research.ucc.ie.
- NutraIngredients (2021). Study: Lactobacillus plantarum reduces depression and improves sleep in insomniacs. NutraIngredients. nutraingredients.com.
- Śliwka, A. et al. (2025). Psychobiotics in depression: sources, metabolites, and treatment, a systematic review. Nutrients. mdpi.com.
- King's College London (2023). New data demonstrates potential role of probiotic supplementation in adults with major depressive disorder. King's College London. kcl.ac.uk.
- Sá Filho, A.S. et al. (2026). Attacking the gut brain axis with psychobiotics: an umbrella review of depressive and anxiety symptoms. Pharmaceuticals. mdpi.com.
- University College Cork (2022). New study shows stress can be reduced by a psychobiotic diet. University College Cork. ucc.ie.
