Gut bacteria need to blamed for anxious feelings

You may have to stop taking antidepressants or another medicine to treat your anxiety, as a new study has found that gut bacteria actually plays a major role in anxious feelings.

A team of scientists discovered that certain gene regulators in the brain - called microRNAs - play a key roll in anxiety-type illness and behaviour, which are affected by bacteria levels in the gut.

Researchers from the University College Cork in Republic of Ireland found that a significant number of miRNAs were changed in the brains of microbe-free mice.

These mice are reared in a germ-free bubble, typically displaying abnormal anxiety, deficits in sociability and cognition and increased depressive-like behaviours.

Corresponding author Dr. Gerard Clarke said, "Gut microbes seem to influence miRNAs in the amygdala and the prefrontal cortex."

"This is important because these miRNAs may affect physiological processes that are fundamental to the functioning of the central nervous system and in brain regions, such as the amygdala and prefrontal cortex, which are heavily implicated in anxiety and depression," Clarke added.

miRNAs are short sequences of nucleotides (the building blocks of DNA and RNA), which can act to control how genes are expressed.

miRNA dysregulation or dysfunction is believed to be an underlying factor contributing to stress-related psychiatric disorders, neurodegenerative diseases and neurodevelopmental abnormalities.

The researchers found that levels of 103 miRNAs were different in the amygdala and 31 in the prefrontal cortex of mice reared without gut bacteria (GF mice) compared to conventional mice.

The findings suggest that a healthy microbiome is necessary for appropriate regulation of miRNAs in these brain regions.

This suggests that even if a healthy microbiota is present in early life, subsequent changes in adulthood can impact miRNAs in the brain relevant to anxiety-like behaviours, the authors noted.

Dr. Clarke said: "This is early stage research but the possibility of achieving the desired impact on miRNAs in specific brain regions by targeting the gut microbiota -- for example by using psychobiotics -- is an appealing prospect."

The study appears in the Microbiome journal.