More and more people are suffering from depression – and not just since the pandemic. A new Swiss study now shows how probiotics can have a positive effect on the treatment of depression. Because the gut and the brain are interconnected.

Depression is one of the most common diseases and one of the most underestimated in terms of its severity. According to the German Depression Aid Foundation, 8.2 percent of Germans suffer from a chronic depressive disorder. That is the equivalent of 5.3 million adults, not including the figures for affected children and young people under the age of 18 and people over 79 years of age.

As the WHO disclosed in a report in 2017, the number of depressive illnesses is steadily increasing. It can be assumed that the corona pandemic has also increased the number of cases. It is all the more important to continue researching effective treatment methods for depression. So far, the primary focus here has been on antidepressants and psychotherapy.

A new study by the Psychiatric University Clinic in Basel now shows the supportive effect of probiotics in the fight against depression. Probiotics are medicinal preparations that contain viable microorganisms, which in turn can have a beneficial effect on the intestinal environment.

As part of the study, subjects suffering from severe depression were divided into two groups. While the first group received a probiotic with lactic acid bacteria for a month – in addition to the usual dose of antidepressant – the second group only received a placebo in addition to the antidepressant.

The result: The subjects who took probiotics had a significantly better mood than the comparison group. In addition, the brain activity of the subjects also changed, as shown by MRI images. Certain brain regions for emotional processing are structured differently in depressed people than in healthy people. After taking the probiotics for 31 days, this brain activity returned to normal, while it remained the same in the control group.

A confirmation for the researchers, because the psyche and intestines are connected, has been certain for several years: “Our results indicate that additional treatment with probiotics improves the depressive symptoms and increases specific health-related bacterial taxa,” write the study authors.

The improvement in the mental state of the participants is related to the so-called gut-brain axis. It describes the connection between the nervous system of the digestive tract and that of the brain – they are in exchange and can even influence each other.

Since messenger substances such as neurotransmitters, hormones and short-chain fatty acids are also involved in the communication between the gut and the brain, the condition of the gut can also affect mental well-being – and vice versa. The so-called vagus nerve, which regulates the activity of almost all internal organs, plays a central role here.

In other words: if we feel bad mentally, we also feel it in our digestion. If the intestinal flora gets out of balance as a result (or due to poor diet and lifestyle habits), we also notice this on a mental level – we are tense, react more sensitively to stress and are in a bad mood.

It is known that acute stress and anxiety situations can lead to abdominal pain, loss of appetite, nausea or even diarrhea. In the worst case, stomach ulcers can develop – just because the head sends to the intestines that we are not feeling well – a real vicious circle.

The effect of the probiotics can also be explained with the help of the compound. Taking probiotics with lactic acid bacteria (lactobacilli) increased the proportion of good intestinal bacteria in the subjects.

Like bifidobacteria, lactobacilli can produce important messenger substances, including GABA and serotonin, which in turn have a relaxing and anxiolytic effect. The composition of the intestinal flora can therefore influence our psyche and our state of mind.

But: After stopping the probiotics, the number of positive intestinal bacteria also decreased, the study authors emphasize. This indicates that a long-term intestinal cure is necessary in order to be able to treat depressive symptoms concomitantly.

Our PDF guide explains how you can prevent digestive problems and treat intestinal diseases properly.

A study by the Catholic University of Leuven in Belgium from 2015 with more than 1000 subjects also shows that depressed people lack certain types of intestinal bacteria – these include coprococcus and dialister. The former strain of bacteria has a signal path to the neurotransmitter dopamine, which provides more drive and motivation. Coprococcus also produce the anti-inflammatory butyrate. The latter – like bifidobacteria or lactobacilli – are among the “good intestinal bacteria”.

A study by the Chongqing Medical University in China from 2020 also confirms the findings of the new study: “We already knew that depressed people have fewer bacteria that produce so-called short-chain fatty acids. At the same time, microbes that can trigger inflammation in the body are becoming more common.

According to the study results, the balance of the bacteria and the composition of their metabolic products as well as the variety of viruses and fungi that also live in the intestine are shifting.

The targeted use of certain probiotics can therefore support the treatment of depression. However, they in no way replace an antidepressant or psychotherapy, as the authors of the current study emphasize.

In the case of a mental illness such as depression, the primary aim is to solve the cause of the problem and to work proactively on current thought patterns and behaviors. But: “With additional knowledge about the specific effects of certain bacteria, it may be possible to optimize the selection of bacteria and use the best mixture to support the treatment of depression,” says the study.