A family study of schizotypal disorder.

Direct, blind interviews were used to study the risk for and prevalence of DSM-III-R Axis I and II disorders in 93 first-degree relatives of outpatients with schizotypal personality disorder (SPD) and outpatients with other personality disorders. Risks for SPD (at a slightly loosened diagnostic threshold) and schizoid personality disorder were significantly higher in the families of probands with SPD. Schizophrenia was present only among relatives of probands with SPD, accounting for a morbid risk of 4.1 percent. Neither familial risks for mood and anxiety disorders nor the prevalence of other Axis II disorders significantly differed in the two groups of relatives. It is suggested that SPD is a familial disorder representing a phenotypic expression of liability to schizophrenia.