In fact, psychiatrists are now exploring the possibility of manipulating these microscopic populations with the goal of treating clinical depression and anxiety -- all without resorting to potentially harmful pharmaceutical drugs.

The mind-gut connectionThe bidirectional link between the emotions and the gut is nothing new. Scientists have long known that the enteric nervous system (ENS) found within the gut is connected to the brain via the vagus nerve, and is so influential that it's often referred to as the "second brain." When we experience sadness, fear or another emotional state, the gut is affected.