Do Probiotics Treat Depression?

Depression continues to plague the civilized world, and it has already become a threat in some societies. It is a serious mental condition, and its consequences are devastating. At best, it ruins our performance, robs us of nearly all joys of life, and turns what was once an enjoyment into dull routine. At worst, it paints our whole life black and evokes suicidal thoughts.

A new cure is coming!

Most today’s antidepressants’ effect lies in regulating neurotransmitters’ work inside the brain. However, over the past decade, scientists have discovered a connection between the central nervous system and the gastrointestinal tract. Particularly, our mental state is likely to depend on intestinal microbiotic composition. It has been observed that in some cases changes in mental state go side by side with changes in the microbiome. This creates a basis for the development of new methods and drugs intended for treatment of depression and other mental disorders.


The ultimate goal of this effort is to replace today’s therapy methods with a new one. It is expected to directly target the cause of depression, take less time to produce the curative effect, and eliminate side effects. Scientists are taking a closer look at interconnections between the gastrointestinal, enteric nervous, immune, endocrine, and other systems. It is no great secret that our mental health largely depends on what we eat, so researchers are digging deeper to get to the core. They have applied probiotics (Lactobacillus) – microbes, which are compatible with and beneficial for the human body.

Laboratory rodent studies have revealed a decrease in stress hormones (adrenaline, noradrenaline, adrenocorticotropic hormone, serotonin, etc.) in species that received doses of probiotics. It signifies their ability to suppress the so-called “hypothalamic-pituitary-adrenal axis”, which is hyperactive during a depression. Also, probiotics act as antioxidants and improve absorption of various healthy nutrients.

Scientists at the UVA Department of Neuroscience have discovered that stress and depression strip gut microbiome of Lactobacillus. Every time a patient showed an increase in depression symptoms, he/she showed lower Lactobacillus levels. As the team studied the mechanism, they found that these microbes could influence the level of kynurenine, whose pathway of tryptophan metabolism mediates factors contributing to depressive disorders. When Lactobacillus levels increase, those of kynurenine decrease, and so do symptoms of depression.


These are results of preclinical studies. Some clinical studies, which involved treatment with probiotics, have been completed and there were positive results. Studies were grouped to separately to evaluate different characteristics, which are immediately affected by depression: mood, stress/anxiety, and cognitive abilities. Of five studies that focused on mood, two revealed improvements; of seven studies focusing on stress/anxiety, two ended positively; all three studies focusing on cognitive abilities proved effective. The duration of a study ranged from 3 weeks to 6 months.

This appears to be a good portion of fuel for budding nutritional psychiatry. The new findings indicate that probiotics’ potential extends far beyond treating intestinal disorders. The discovery of the intestine-brain relationship paves the way for a new way of treatment of depression – dietary treatment, which is going to be painless and, hopefully, side-effect-free.

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