Close this search box.
Close this search box.
Close this search box.

Psychobiotics and Our (Second) Brain

AUTHOR: Andrija Karačić, M.D., specializing in abdominal surgery and the founder of the Gut Microbiome Center in Zagreb

Modern science is researching the complex connection between the gut and the brain and the development of psychobiotics, microorganisms that can have a positive effect on mental health. Research to date shows that psychobiotics support the digestive system and help to reduce mental fatigue and a general feeling of tiredness, thus promoting overall mental health.


Even with significant advances in science, we still do not fully understand how the human brain functions. Emotional health, psychological, and neurodegenerative diseases remain areas filled with mysteries and open questions. However, it becomes even more complex when we include the so-called second brain in the story. Modern science claims that we possess not one but two brains. The popular term “second brain” refers to an independent, complex nervous system in the lining of our intestines. The first and second brains communicate with each other through different neurohumoral signals via the gut-brain axis. This means that both the brain and the intestines quickly learn when their partner on the other side of the axis is in trouble.

Today, scientists and clinicians, in addition to discovering how the gut-brain axis functions, are also working on finding methods to treat this axis and related diseases. Cognitive-behavioural psychotherapy, antibiotics, and faecal transplantation are often mentioned in this context. A less radical but equally effective method could be the use of psychobiotics.

Have you heard of psychobiotics?

Considering that many scientific papers have been published on the topic of probiotics and the gut-brain axis, the field of psychobiotics has only “exploded” in the last decade. Before 2013, there was not a single scientific paper on this topic, and in 2022, as many as 72 publicly available scientific papers were published exclusively on the topic of psychobiotics.

Psychobiotics were defined by a group of scientists from the University of Cork in Ireland, a leading global centre for studying the gut-brain axis, as far back as 2013. Similar to probiotics, psychobiotics are living microorganisms that, when ingested in sufficient quantities, have beneficial effects on the body. In the case of psycho-probiotics, they have an impact on mental health. This subset of probiotics has the capacity to produce and deliver neuroactive substances, neurotransmitters, and neuromodulators such as serotonin, the “happiness” hormone, and GABA. Because of this, these microorganisms can influence the functioning of the gut-brain axis, primarily the function of the vagus nerve. In addition to the vagus nerve as the main anatomical axis of the gut-brain connection, psychobiotic metabolites reach the “first” brain through circulation, or indirectly through the spinal cord, or directly through the blood-brain barrier.

In addition to the secretion of neuroactive metabolites, psychobiotics achieve their effects through anti-inflammatory actions and by their ability to reduce the activity of the hypothalamic-pituitary-adrenal axis due to the neuroendocrine action of their metabolites.

At that time, the definition of psychobiotics was primarily based on the results of preclinical research on laboratory animals, which suggested the potential of psychobiotics in the treatment of depression and anxiety. In humans, the effects of psychobiotics have been mainly investigated in collaborative psychiatry, particularly in the treatment of somatic diseases such as irritable bowel syndrome.

These days, we already have the first meta-analyses in the field of psychobiotics. Several meta-analyses have pointed to the effectiveness of psychobiotics in reducing symptoms of depression. For instance, one meta-analysis of 10 randomized placebo-controlled studies that investigated the impact of psychobiotics in alleviating symptoms of major depressive disorder showed that psychobiotics are indeed significantly more effective than a placebo, especially in male patients and with longer-term therapy. However, a meta-analysis of 12 randomized placebo-controlled studies did not demonstrate the same effectiveness of psychobiotics in treating anxiety, similar to the meta-analysis on psychobiotics in the treatment of anxiety in young individuals. A review of the literature gives the impression that psychobiotics are more effective in treating depression than anxiety. It is believed that psychobiotics are particularly effective in treating depression because their anti-inflammatory action influences its inflammatory component.

On the market, there are products that contain psychobiotics whose efficacy has been scientifically proven.

OMNi-BiOTiC® STRESS contains 9 different bacterial strains of human origin, the effectiveness of which has been scientifically demonstrated through clinical studies. Numerous research studies have shown its positive impact not only on gastrointestinal issues but also on reducing mental fatigue and overall tiredness, as well as on improving sleep. The addition of B-group vitamins, it protects cells from oxidative stress and contributes to normal psychological function and the normal functioning of the nervous system, normal metabolism, energy production, reduction of fatigue and exhaustion, and the normal function of the immune system.


Dinan et al., 2013,

Misera et al., 2021,

Liu et al., 2018,

Kadosh et al., 2021,

Nadeem et al., 2019,

Sikorska et al., 2023,


Centar Mikrobiom Ltd.

Sky Office, Toranj B

  1. F. Mihanovića 9, Zagreb, Croatia

Mob.: + 385 98 13 73 344

Share the Post:

Related Posts

Medicinal Plant Chicory

Chicory (Cichorium intybus L), a perennial herbaceous plant, is widespread throughout Europe. It is rich in inulin, which acts as a prebiotic and stimulates the growth of beneficial bacteria in the intestinal microflora.

Read More