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."

Read on for detail.....
http://www.medicalnewstoday.com/healthnews.php?newsid=66840
A post on 4-17-07 from Dr. Mercola