Exposure to certain forms of soil bacteria can boost the immune system, which can in turn improve mood as effectively as antidepressant drugs.
Mice exposed to a benign soil microbe, Mycobacterium vaccae, performed better on a behavioral task commonly used to test the effectiveness of antidepressants.
The mice were placed in water and observed to see how long they continued swimming before giving up. The mice who had been exposed to Mycobacterium vaccae continued swimming for a much longer time.
These results are similar to those from a previous study, in which human cancer patients treated with the bacteria reported significant improvements in their quality of life.
Researchers suspect that the microbes are affecting the brain indirectly by causing immune cells to release chemicals called cytokines, which stimulate the production of the mood-regulating chemical serotonin.
The lead researcher on the study, Chris Lowry, added that, "These studies help us understand how the body communicates with the brain and why a healthy immune system is important for maintaining mental health.
They also leave us wondering if we shouldn't all be spending more time playing in the dirt."
Neuroscience March 28, 2007
MSNBC April 13, 2007
Medical News Today April 2, 2007