Depression is taking a staggering toll on the modern world. Around 10 percent of the population can expect to become clinically depressed over the coming year. And things are likely to become worse. The World health Organization estimates that depression will impose the second-biggest health burden globally by 2020. Think about that for a moment. Depression will impose a bigger burden than heart disease, arthritis and many forms of cancer on both individuals and society in less than a decade. Prof Mark Williams