Psychobiotics are live bacteria (probiotics) which, when ingested, confer mental health benefits. Research has increasingly shown that good mental health comes not just from our environment, lifestyle and relationships, but also from the bacteria in our gut (see this review article). As such, psychobiotics have piqued interest from researchers worldwide as they seek to uncover more about how these microorganisms might be able to shape our biology, psychology, and behavior.
How Do Psychobiotics Work?
Psychobiotics appear to benefit mental health by influencing the biochemistry of our brains.
For example, in animal studies, ingesting the L. plantarum PS128 psychobiotic has been observed to alter the levels of serotonin and dopamine in the brain. These neurotransmitters are involved in mood regulation, reward pathways, and anxiety reduction. A different psychobiotic strain appears to influence the expression of genes in the brain related to GABA signaling, which also plays a key role in stress response.
Psychobiotics appear to do this work via the gut-brain axis. The gut-brain axis is a bidirectional communication system between the gut and the brain. It connects the digestive organs with the central nervous system via the bloodstream, vagus nerve, and immune system. This complex symphony of exchanges manages our appetite, our mood, and even our capacity to cope with stress.
Gut microbes are able to biosynthesize many molecules, transforming amino acids that we eat into neurotransmitters, reactivating steroid hormones that cycle through the gut, and creating a wide variety of other potential signaling molecules.
Animal studies suggest that signaling molecules produced by psychobiotics, such as secondary bile acids, polyamines, and polyphenols, may make their way from the gut, into the bloodstream, across the blood-brain barrier (BBB) and into neurons of the brain to exert their effects directly.
How psychobiotic bacteria residing within the gut can influence gene expression in the brain is far from understood. However, the vagus nerve, which connects the brain and the gut, may be one possible conduit for such “at a distance” effects of psychobiotics.
For example, bacteria that synthesize indoles from amino acids within the gut exert an effect on mental health in animals, but only when the vagus nerve is intact. This suggests that indoles signal to the brain via the vagus nerve rather than traveling from the gut to the brain.
While certain psychobiotics also enteroendocrine cells of the gut lining produce neurotransmitters within the gut, these gut-derived neurotransmitters are not believed to travel to the brain. The effects of gut serotonin on neurotransmitter levels within the brain, for example, could be mediated by vagus nerve signaling; further studies will help to clarify this question.
Psychobiotic metabolites such as short-chain fatty acids (SCFAs) may affect immune cells that are activated by chronic stress, dampening their release of pro-inflammatory cytokines. Cytokines have targets within the brain, specifically the metabolism of brain neurotransmitters. Immune dysregulation is associated with psychiatric disorders. The ability of a psychobiotic to support a healthy immune response could therefore account for its effects on mental health.
What Effects can Psychobiotics Have on Mental Health?
The microbiome can influence mental health in a variety of ways. In some cases poor mental health is caused or exacerbated by poor gut health. Combating the effects of pathogenic organisms in the gut by taking a gut-health probiotic or increasing the amount of prebiotic foods in your diet may therefore contribute to better mental health.
Psychobiotics are believed to influence mental health not (only) by repairing gut health, but by other mechanisms as well. They appear to do so in both the absence and presence of gut health problems. One excellent example of such a psychobiotic is Lactobacillus plantarum PS128 (PS128).
In one study, PS128 was given to healthy individuals with self-reported insomnia. They were randomly assigned to receive either PS128 or a placebo. After 30 days, participants in the PS128 group exhibited significant improvements in mood compared to the placebo group, as measured by a standardized assessment scale.
The study also observed improvements in sleep quality among participants in the PS128 group. PS128 supplementation was associated with enhanced sleep quality, specifically less waking in the night. Another study of highly stressed information technology (IT) specialists demonstrated benefits of PS128 on perceived stress and improvements in sleep.
What Are Examples of Probiotic Strains That Are Considered Psychobiotics?
Not all probiotics are psychobiotics. To be potentially classified as a psychobiotic, a bacterial or yeast strain should be supported by clinical research that suggests a beneficial effect on mental health at a specific dose.
The following list includes known psychobiotics, their benefits, and published research. It should not be considered exhaustive. Many of the listed strains can be found online or at health food stores in various formulations, including capsules, tablets, powders, and chewable tablets.
Lactobacillus rhamnosus CNCM I-3690
Reduced stress of public speaking1
Lactobacillus helveticus R0052 and Bifidobacterium longum R0175
Appears to reduce cortisol levels, which is strongly associated with stress.2-4
Lactobacillus casei Shirota
May inhibit anxious thoughts or feelings.5
Lactiplantibacillus plantarum PS128 (formerly Lactobacillus plantarum)
Appears to reduce stress and improve sleep quality in clinical studies– possibly by influencing dopamine and serotonin levels as suggested by preclinical studies.6-7
Psychobiotics vs Nootropics – What’s the Difference?
Psychobiotics and nootropics can both be used to enhance brain function, often in different ways.
Nootropics are supplements that enhance cognitive function, memory, and focus. They are sometimes referred to as "cognitive enhancers" because they are believed to have a positive impact on brain function. Nootropics can include medications, but they can also be natural substances such as ginkgo biloba, caffeine, and mushrooms such as lion’s mane and cordyceps. Nootropics are used by a wide range of individuals, including students, professionals, athletes, and older adults who are looking to improve their cognitive performance.
Psychobiotics, on the other hand, are known primarily for having a positive impact on mood. These probiotic bacteria may influence the activity of neurotransmitters and other compounds that can have a positive effect on mood, anxiety, and stress levels.
Notably, some probiotics appear to provide nootropic / cognitive benefits, just as some probiotics appear to have psychobiotic benefits on mental health. However few cases to date have noted both benefits from a single probiotic strain. In the future as more strains are studied with regards to both cognitive and mental health benefits, more psychobiotics that are also nootropics may be discovered.
How to Get Started With a Psychobiotic
When starting a psychobiotic regimen, it is recommended to consider the following steps:
- Consult with a healthcare professional: Before starting any new supplement or medical food, it is advisable to consult with a healthcare professional, especially if you have any underlying health conditions or are taking medications. They can provide personalized guidance and help monitor your health as your body and mind adjust to the psychobiotic you choose.
- Choose an appropriate strain: Based on your specific requirements and the potential benefits you seek, select a psychobiotic strain that aligns with your goals. Consider factors such as the strains' scientifically documented effects, safety profile, and any relevant research studies.
- Select a reliable product: Look for reputable probiotic brands or manufacturers that have a track record of producing high-quality products. It is important to ensure that the product lists the strain(s) and dosage accurately, and has undergone proper quality control measures.
- Follow dosage instructions: Read and follow the recommended dosage instructions provided on the product label or as advised by your healthcare professional. Consistency is crucial, so aim to take the psychobiotic supplement daily and at the specified dosage.
- Monitor and assess effects: Keep track of any changes or improvements in your mental health and overall well-being while taking the psychobiotic supplement. It may take time to notice significant effects, so it's advisable to maintain the regimen for a sufficient duration.
Remember, individual responses to psychobiotics may vary, and it is important to give the regimen time to assess its effectiveness. If you experience any adverse effects or have concerns, consult with your healthcare professional for further guidance.