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 in need of further research before they constitute a realistic knowledge base. Methodological and conceptual issues should not be underestimated.