Introduction: The Extended Psychosis Phenotype--Relationship With Schizophrenia and With Ultrahigh Risk Status for Psychosis

In clinical practice, psychotic disorders naturally come as diagnosable ‘‘things,’’ categories, the carriers of which form a diagnostic boundary below which reside the healthy noncarriers who do not display the mental phenomena observed in patients. In research, however, the focus is on scientific exploration of the distribution of experiences at all levels of severity in populations and its genetic and nongenetic causes. Population research has shown high rates of psychotic experiences in people who are not readily diagnosable according to ICD/DSM/ RDC criteria—suggesting an ‘‘extended psychosis phenotype,’’ which shares demographic, etiological, familial, and psychopathological factors with clinical psychotic disorder. In fact, affective dysregulation, psychotic experiences, motivational impairments, and cognitive alterationsappeartobedistributed andcoexpressedtoadegree in nonill individuals and have been shown to index risk for later onset of disorder, particularly if they tend to persist over time. 1 (also, R. J. L & J. v. O., unpublished data,