Prospective investigations of the prodromal state of schizophrenia: review of studies

Objective: The paper presents a comprehensive overview of prospective studies monitoring or intervening in the pre-onset phase of first episode psychosis. Method: A systematic literature search was conducted and supplemented by a manual search. All relevant studies were ordered and intensively reviewed according to specified criteria. Methodological and conceptual issues are discussed. Results: Reports of 23 prospective studies were found, some describing subsamples of larger samples. Major methodological and Conceptual divergences exist. Conclusion: Applied criteria detect individuals with a significantly increased risk of psychosis within the schizophrenia spectrum, but these criteria are only validated on clinical populations. The significance of differences in sample-characteristics is unclear. Most study samples are small. Results are preliminary and ill need Of further research before they constitute a realistic knowledge base. Methodological and conceptual Issues should not be underestimated.