Schizotypal symptoms and neurocognitive performance
in siblings of patients with schizophrenia
Sabuwalla, Z., Czernansky, J., & Barch, D.
Patients with schizophrenia manifest deviant patterns of performance on tests of attention, executive function, verbal and visuospatial working memory, and learning and memory (for a review, see Heinrichs & Zakzanis, 1998). Similar patterns can be observed in individuals with schizotypal personality disorder (Cadenhead et al, 1999; Diforio, Walker & Kestler, 2000; Voglmaier et al, 1997), a disorder thought to be behaviorally and genetically related to schizophrenia. Schizotypal traits are partially heritable and are elevated in relatives of patients with schizophrenia (Kendler et al, 1993) as compared to a normal population. Relatives of patients with schizophrenia also show impairments on various measures of cognitive functioning (Cannon et al, 1994, Keffe et al, 1994). Furthermore, they manifest more neuropsychological deficits than relatives of affective psychotic patients (Gilvarry et al, 2001). Thus, schizotypal personality traits and cognitive dysfunction represent potential indicators of a genetic risk for schizophrenia, as both are elevated in first-degree relatives of patients with schizophrenia.
Few studies have investigated the relationship between schizotypy and cognitive function in relatives of patients with schizophrenia, and have produced conflicting results. These inconsistencies can be attributed to various methodological differences, including mixed sampling method (siblings, half-sibling, parents, co-twins), sampling size, variable criteria for assessing schizotypy (interviews, self-report questionnaires, clinical vs. psychometrically derived samples), and limited measures for assessing cognitive deficits. Using an extensive battery of neurocognitive tests and several measures of schizotypy, we will investigate the relationship between the severity of schizotypal symptoms and various measures of cognitive functioning in first-degree relatives of patients with schizophrenia. We hypothesize that performance on neuropsychological tests will be inversely correlated with symptoms of schizotypy, particularly the negative and disorganized symptom clusters. Exploratory analyses will also be conducted to test the effects of age as a moderator between test performance and symptom severity. Such analyses may provide support for the hypothesis that schizotypal symptoms in adolescence may be indicative of a risk factor for developing schizophrenia.