A Search for ‘Schizophrenia Spectrum Disorders’: An Application of a Multiple Threshold Model to Blind Family Study Data

Abstract

Summary: Family data from schizophrenic and control probands were analyzed using a descriptive analysis and multiple threshold models to determine whether a given group of diagnoses made in accordance with ICD–9 was aetiologically related to schizophrenia. The proportion of relatives receiving any psychiatric diagnosis, other than schizophrenia and affective disorder, was essentially the same between the two study groups. Furthermore, the data did not fit the multiple threshold model tested. Thus, the hypothesis that schizophrenia and a spectrum of disorders defined according to ICD–9 have a common familial aetiology was not accepted.