Transition to schizophrenia and related disorders: toward a taxonomy of risk.

The early detection and prevention of schizophrenia and other psychotic disorders are receiving rapidly growing attention subsequent to the suggestion that poorer outcome is associated with delayed onset of treatment among patients in their first psychotic episode. Although the first generation of so-called "prodromal" research programs has produced encouraging preliminary results, more information is necessary on the conversion rates from prodromal states to schizophrenia in specific samples. Early recognition and prevention strategies require a new taxonomy that classifies subjects by their status of risk of imminent onset of psychosis. Without additional knowledge of the mechanisms through which particular constellations of vulnerability factors, precursors, and prodromal symptoms predict the onset of schizophrenia, it is difficult to judge the effects of existing programs. In this paper, we discuss three sets of issues that will need to be resolved before these preventive programs can be implemented into routine care: (1) optimization of predicting the onset of psychotic disorders; (2) development and evaluation of alternative treatment strategies depending on the presenting risk status; and (3) evaluation of costs and benefits of identifying subjects at risk of psychosis/schizophrenia and receiving a specific preventive treatment.