Ten-year stability of self-reported schizotypal personality features in patients with psychosis and their healthy siblings.

Schizotypal personality disorder (SPD) symptoms or features are common in patients with psychosis and their healthy relatives. However, the long-term stability of these SPD features and therefore their constituting enduring traits underlying vulnerability to psychosis remain to be clarified. Thirty-two patients with psychotic disorders and 29 of their healthy siblings were included from the long-term follow-up study of 89 nuclear families. Participants were clinically assessed by means of a semi-structured diagnostic interview, whereas the Schizotypal Personality Questionnaire-Brief (SPQ-B) was applied for the self-assessment of SPD symptoms. The assessments were carried out upon admission to the study and at follow-up, about 10 years later. The patients had higher scores than their siblings on the SPQ-B both at baseline and follow-up. In addition, self-reported SPD symptoms remained stable over time in total scores and in all the SPQ-B subscores, except for the SPQ-B Disorganization subscale. Self-reported SPD symptoms were stable over the long term among patients with psychotic disorders and their healthy siblings. This finding provides new support for including the SPD construct as a trait measure for studies addressing both vulnerability to psychosis in first-degree relatives of patients with psychosis and long-term persistence of symptoms in patients suffering from psychosis.