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."

Dr. Mercola's Comment:

Antidepressants can compromise your immune system -- which is only one of their many potential harmful side effects. But this interesting new study suggests that getting dirty while working  in your garden can actually provide benefits similar to what antidepressants are promoted to have.

In fact, it will likely provide more benefits than any antidepressant will. Antidepressants likely do not work in the majority of patients that use them. So why do so many clinicians report success stories of using them? Because up to 75 percent of the response of antidepressants can be duplicated by a placebo.

Better to pursue a hobby like gardening that can produce great benefits for your health naturally than to rely on drugs that provide no meaningful upside whatsoever, and certainly in no way, shape or form treat the underlying cause of the disease.

Some other safer, healthier options that have nothing at all to do with taking a pill:

• Take a high-quality fish oil or krill oil. If you haven't read Dr. Stoll's book on this subject, it is highly recommended. He is an enlightened Harvard psychiatrist who has written an outstanding book on the topic.

• Start an exercise program today, as it clearly is one of the best-kept secrets for depression.

• Learn how to use an energy psychology tool like the Emotional Freedom Technique. Energy psychology tools are one of the most powerful methods I know of and really are a crucial element of a successful treatment program.