Getting out and playing in the dirt makes people happy. I'd never doubted it, but a study published earlier this year proves it.

The very title of the original study -- "Identification of an immune-responsive mesolimbocortical serotonergic system: potential role in regulation of emotional behavior" -- is impenetrable, but this article in Discovery gives a good summary of the research and findings. The bottom line: research shows that a bacterium in dirt makes the body produce seratonin, the chemical associated with feelings of happiness and well-being. I'm happy that my friend Margo mentioned it to me, because I hadn't heard of the study when it first made the news earlier this year.