 They rise and fall together. It seemed curious, and I began to understand it only when, in Canada, I sat down with Robert Kohlenberg, a professor of psychology. He, too, once thought that depression and anxiety were different things. But as he studied it for over 20 years now, he discovered, he says, that the data are indicating that they're not distinct. In practice, quote, the diagnoses, particularly depression and anxiety, overlap, end quote.