In 1845 Griesinger declared that mental disorders were physical in origin (Kendell, 2001). The discovery of the bacterial cause of general paresis and the anatomical basis for Alzheimer's disease seemed to confirm this belief. However, is it still reasonable, a century later, to continue to devote increasing amounts of financial and expert human resource to pursuing further possible physical causes for mental disorders? The belief that there remain undiscovered and important biological causes for mental disorders continues to exert a major influence on the direction of research, practice and public education. But has it helped us to understand aetiology, improve management or destigmatise mental disorders?