Kurt Hahlweg & Eckhart R. Straube 
Schizophrenia 
Concepts, Vulnerability, and Intervention

Schizophrenia remains the most complex, puzzling, and because of its tendency towards chronicity, the most severe of the mental disorders. It is a very heterogeneous disorder characterized by extreme disruptions of thought, per- ception, behavior, and emotion. About I % of the population worldwide will experience at least one schizophrenic episode. Most of the patients will have a number of exacerbations leading in about 30% of cases to a chronic residual state, due either to the illness itself or to psychosocial environmental factors, or-most likely-to the interaction of both. Given the enormous personal hardship for patients and their relatives as well as the staggering costs of the illness for our societies, research in schizo- phrenia has become the number one priority in many countries, especially in the United States. However, research on the etiology of schizophrenia has failed to establish a single causal factor, and it is nowadays accepted to be multifactorial. A combjnation of biological predisposition and enviromnental circumstances is assumed to be necessary for the manifestation of the illness. This shift in orientation away from an either/or (biological or environmental, e.g., family interaction) point of view, as evident in the work of the 1950s and 1960s, was certainly desirable to encourage research.