SELF-REPORT MEASURES OF SCHIZOTYPY AS INDEXES OF FAMILIAL VULNERABILITY TO SCHIZOPHRENIA

While structured psychiatric interviews have generally succeeded in id entifying higher rates of schizotypal personality disorder in relative s of schizophrenia versus control probands, self-report questionnaires designed to assess schizotypy have been less successful at distinguis hing these groups of relatives. In the Roscommon Family Study, an epid emiologically based, case-controlled study conducted in the west of Ir eland, relatives were administered a short form of Eysenck's Psychotic ism scale and shortened and modified versions of the scales for magica l ideation and social anhedonia developed by Chapman and colleagues. W e compared, with relatives of matched controls, relatives of four prob and groups: schizophrenia, other nonaffective psychoses (ONAP), psycho tic affective illness (PAI), and nonpsychotic affective illness (NPAI) . Only social anhedonia scores successfully differentiated, at modest levels of significance, relatives of schizophrenia versus control prob ands. Levels of magical ideation did not distinguish relatives of schi zophrenia, ONAP, PAI, or NPAI probands from relatives of controls. Com pared to controls, ONAP probands had significantly elevated psychotici sm scores, but no such increase was seen in relatives of schizophrenia , PAI, or NPAI probands. Dimensions of schizotypy assessed at personal interview were significantly better at differentiating relatives of s chizophrenia and control probands than our measures of social anhedoni a, magical ideation, or psychoticism. Although psychiatric interviews in this sample have shown that clinically assessed schizotypal persona lity disorder and traits strongly aggregate in relatives of schizophre nia patients, of the three self-report instruments designed to assess schizotypy, only one even modestly identifies relatives of schizophren ia versus control probands. These results suggest that, compared with psychiatric interviews, self-report questionnaires are less successful at assessing underlying familial vulnerability to schizophrenia.