The Relation Between the Intestine and the Brain
The intestine and the brain are connected. This connection is called the brain-gut axis. The brain-gut axis involves communication via neural, endocrine, and immune pathways between the brain and the intestine. Recently, it has become clear that the microbiota (the bacteria in the intestine) also play a role in this communication. The microbiota produces neuroactive substances and their precursors, reaching the brain via endocrine and autonomic pathways. Bacterial products, such as gram-negative endotoxins, can also influence mood and cognitive functions via indirect and direct mechanisms.
What is Cognitive Reactivity?
Cognitive Reactivity is a measure of how much you think about sad things. People who are more likely to get depressed have more of these thoughts. Studies have shown this by looking at people who have never been depressed before and followed them for a while. This means that if we can stop people from thinking so much about sad things, we might help them not become depressed.
Some hypotheses of studies say that probiotics can help with reducing stress and anxiety. There is some evidence that this is true from studies of animals and some humans. For example, one study found that mice with a probiotic drink felt less anxious and stressed. Another study found that rats that had a probiotic drink felt less depressed. People who took a probiotic for 3 weeks felt better about their moods than people who didn’t take a probiotic. Another study found that people with chronic fatigue syndrome felt less anxious after taking a probiotic for 2 months.
How Multispecies Probiotics can help changes in Mood
Multispecies probiotics (strains of different genera) can be more effective because of the other properties of each strain. For example, they can colonize different niches, adhere better, and work in a range of pHs. However, different probiotics can compete, so this needs to be tested on a case-by-case basis.
Perceived cognitive Reactivity to transient changes in sad mood was measured by the revised Leiden Index of Depression Sensitivity before and after the probiotics intervention. It was hypothesized that the probiotics intervention would lower the activation of negative thoughts that accompany sad mood.
The Study on Multispecies Probiotics and Mood Chab
20 participants without a mood disorder took a probiotic food supplement for 4 weeks. 20 other participants took an inert placebo for 4 weeks. The participants’ cognitive Reactivity to sad mood was assessed before and after the 4 weeks.
Participants who received the 4-week multispecies probiotics intervention showed a significantly reduced overall cognitive reactivity to sad mood. This was largely accounted for by reduced rumination and aggressive thoughts.
ANOVAs showed that the LEIDS-r total score, aggression, and rumination changed over time depending on whether someone took a probiotic or not. People who took a probiotic for 4 weeks had lower scores on the LEIDS-r total score, aggression, and rumination after 4 weeks than before. Thus, the study showed that probiotics can help reduce aggressive and ruminative thoughts.
Results show that probiotics may help reduce negative thoughts when feeling sad. This is the first evidence of this and needs more research to see if it could be used to prevent depression.