The link between gut bacteria and mood and anxiety received strong scientific support during a series of presentations at the recent meeting of the American College of Neuropsychopharmacology.
“Current state-of-the-art research in both animal models as well as humans point to the link between the gut microbiota and mood and anxiety models, as well as the potential for psychiatric medications to directly affect the gut microbiome,” said Dr. Vicki Ellingrod, chair of this session.
The gut-mood connection was most profoundly demonstrated during a study in which researchers measured the microorganism changes in rats’ gastrointestinal systems as the rats were subjected to chronic stress for seven weeks. Not only did the number of microorganisms decrease as stress became more chronic, behavioral changes suggested that the rats also began experiencing loss of pleasure and “despair-like” behavior.
When these microorganisms were transferred from the stressed rats to a new group of animals that had not been stressed, Dr. Emily Jutkiewicz found that these new animals also began to exhibit these same despondent behaviors after five days, suggesting that a change in gut bacteria may directly cause mood and behavior changes.
Furthermore, a series of human studies explored the treatment implications of the gut-mood link. The researchers found similar reductions in the microbiome in participants suffering from both major depression and bipolar disorder. These changes were linked to greater levels of anxiety and sleep problems as well as increased reports of general health problems.
“The data support the hypothesis that targeting the microbiome may be an effective treatment paradigm for bipolar disorder,” said Dr. Simon Evans.
Researchers also discussed the role of medications during the final two presentations. By studying individuals over time, Dr. Chadi Calarge was able to examine microbiome changes when individuals were depressed or in remission, and when they were and were not receiving anti-depressant medications (SSRIs).
While no changes in gut bacterial diversity were observed in patients with depression, the researchers did find species-level differences. Furthermore, starting SSRI treatment was associated with an increase in the production of indoles, suggesting changes in tryptophanase-producing bacteria.
New evidence also indicates the presence of increased intestinal permeability in depression, potentially leading to increased bacterial translocation.
Finally, one of the troubling side effects of atypical antipsychotic (AAP) medication is how it changes the body’s ability to metabolize energy, often resulting in weight gain. Dr. Stephanie Flowers demonstrated how female bipolar patients who gained weight with AAP treatment had a greater reduction in microbiome diversity than did female bipolar patients who were being treated with the same medications but did not gain weight.
This finding suggests that the health of our gut may also put us at increased risk for certain medication side effects, she said.
Abstract summaries of this research are published in the journal Neuropsychopharmacology.