SCHIZOTYPAL DISORDER - AT THE CROSSROADS OF GENETICS AND NOSOLOGY

The aim of this paper is to review the available evidence in support o f the correctness of including the DSM-III/III-R schizotypal personali ty disorder (SPD) in the schizophrenia spectrum, to discuss the compon ents that may account for the familial segregation of SPD, and to cons ider the implications for research and clinical use of this diagnostic category. The majority of the available data from genetic epidemiolog y studies, starting from probands with schizophrenia or with SPD, sugg est that SPD is one of several phenotypes of liability for the schizop hrenia spectrum. Recent twin studies suggest that the affect-constrict ed and eccentric aspects of SPD are the features that truly belong to the spectrum of schizophrenia, sharing important genetic influences. H owever, other components are more useful for the identification of SPD in clinical settings, and these may be the specific focus of treatmen t. The present categorization appears to be a reasonable trade-off for the purposes of both the investigator and the clinician, even though different components within SPD may have different origins and can be selectively emphasized according to the different aims involved.