[F]inding that depression is represented in the brain does not mean that it is a disease, let alone a disease that can be cured by chemically altering the brain. Depression may result from a normally functioning brain, containing neural networks that have been shaped by life events and that respond to current life demands in a way that is experienced subjectively as sadness and despair. It may be the events themselves that make us feel lost and hopeless, or it may be the way in which we have learned to interpret those events. In either case, the underlying brain mechanisms may be normal.
— Irving Kirsch, The Emperor’s New Drugs, p. 100