Depression, which is very common, happens because we don’t have enough feel-good chemicals in our brains. It is all about neurotransmitters, the chemicals neurons use to talk to each other. Not enough of the right ones, then you are depressed. At least, that is what most doctors think, and what they tell their patients. Not University of Cambridge Professor Edward Bullmore. As Professor of Psychiatry, he has seen more mental illness than most, and he isn’t buying the chemicals theory. Depressed brains are inflamed, and he has just written a world wide best seller explaining why. Depression is common in people with inflammatory diseases, like arthritis, obesity (fat is inflammatory), and personal stress (inflammatory again). The science is still developing, but it appears that the best way to avoid depression is to keep your levels of inflammation well controlled.