for Schizotypy (SIS): A Preliminary Report

This article presents a new interview-based research instrument for assessing schizotypal symptoms and signs. The Structured Interview for Schizotypy (SIS), which was developed from experience gained in a large, controlled family study of schizophrenia in the west of Ireland and has been field-tested in three other locations, differs from previously available interviews in that it includes: (1) built-in contex-tual assessments of the pathological nature of certain symptoms (e.g., suspiciousness or ideas of reference); (2) multiple in-dependently scored items, most with closed response options, per symptom scale; (3) extensive assess-ment of schizotypal signs; (4) symp-tom probes designed to make responding positively appear nondeviant; and (5) coverage of potentially relevant symptoms and signs not required in current criteria for schizotypal personality disorder. Schizotypal symptoms can be assessed with high reliability by the SIS. When sufficient variability is present, schizotypal signs are also reliably assessed by the SIS, although the reliability is generally lower than that found for symp-toms. In three independent pilot studies, schizotypal symptoms and signs assessed by the SIS appear to discriminate significantly the relatives of schizophrenic patients from relatives of controls. The belief that schizophrenia-like personality disorders aggregate in relatives of schizophrenic patients can be traced back to Kraepelin and Bleuler (Kendler 1985). During the last two decades, a number of con-trolled family and adoption studies have documented an increased risk for these disorders in biological relatives of schizophrenic patient