Schizophrenia is a disorder at the heart of concepts of “madness” but one that is difficult to define precisely because it is variable in expression and severity. Until recently it was classified as a functional disorder, meaning that no organic basis was known. It was distinguished from the other main group of functional psychoses, the affective or emotional disorders, over a century ago. Schizophrenics may be emotionally disturbed, but the primary problem is one of thought rather than emotion. There is often a curious divorce between emotion and thought with inappropriate laughing, crying or flat unconcern. Running through the various manifestations of schizophrenia are certain core features that involve disorders of speech, thought, belief and social awareness (Frith, 1992). Speech may follow a bizarre train of ideas. Voices may be heard that tell the patient what to do or that talk critically about what the patient is doing. Schizophrenia is a disorder that devastates the individual sufferer, imposes great strain on the family, and is costly to society. It has been attributed to many causes, styles of parenting, society, diet, unknown viruses and genes, but no theory is universally accepted. Evidence from family and adoption studies indicates a genetic influence.