Typical treatments for depression and anxiety include prescription medications and talk therapy, but new research has revealed an unexpected treatment: A strong dose of microorganisms. The human-bacteria relationship is a deeply symbiotic one, says Ted Dinan, a leading expert in the interface between biology and psychiatry and a professor of psychiatry at the University of Cork, Ireland. Dinan says that the approximately 1.5 kilograms of bacteria in the average human gut are “absolutely essential and produce products our brains