Depression does not always respond completely to antidepressants. Often, the response is only partial. What can be done for depressed people in that case?
Usually, adding another medication can solve the problem. However, that can be costly, adds to the side-effect risks, and does not always work.
Finding alternative “add-ons” is an ongoing effort. One intriguing possibility is the use of a probiotic as adjunctive treatment. A study has been done in the United Kingdom by Nikolova and colleagues; the results were were published in JAMA Psychiatry in June 2023.
This was a randomized, double-blind, placebo-controlled trial (high quality research approach). Adults ages 18 to 55 who had a Major Depressive Disorder being treated with an antidepressant with only an “incomplete” response were given a probiotic or a placebo.
The probiotic was a multi-strain version (multiple species of bacteria often found in the normal GI tract). It contained 8 billion colony-forming units per daily dose.
Half of the research subjects took the probiotic daily for 8 weeks; the other half took a placebo (inactive ingredients only).
At the end of the 8 weeks the researchers found that the group taking the probiotic had “… greater improvement in depressive and anxiety symptoms compared with placebo.”
The researchers had anticipated that probiotics were a reasonable option to try because of the known microbiota-gut-brain connection. Microbiota refers to the bacteria normally found in the large intestine, which work synergistically to aid digestion, help regulate the immune system, and provide two-way feedback between the gut and the brain.
This is an exciting research finding. It needs to be replicated with even more research subjects before it is ready for a formal recommendation by the medical community.
Peter M. Hartmann, MD
Family Medicine & Psychiatry
