Personality Dimensions and Cognitive Functioning of Relatives of Persons Diagnosed with Schizophrenia and Bipolar I Disorder: A Comparative and Predictive Study

Abstract

The purpose of this study was to determine a set of personality and cognitive variables that could best be used to predict membership into either a schizophrenia or bipolar relative group. A group of relatives of persons diagnosed with schizophrenia (n = 59) and a group of relatives of persons diagnosed with bipolar I disorder n = 54) were compared along four dimensions of personality and eight dimensions of cognitive functioning. Relative group comparison with a healthy control group (n = 64) along the same personality and cognitive dimensions was a secondary goal. Dimensions of personality were measured using the Structured Clinical Interview for DSM-IV-TR Personality (SIDP-IV) from which trait scores were derived for the cluster A, cluster B, avoidant and obsessive-compulsive personalities. Cognitive functioning was assessed within the domains of attention, working memory, and executive functioning using a variety of measures.

The schizophrenia relative group was best distinguished from the bipolar I relative group on cluster A traits, whereas the bipolar I relative group was best distinguished from the healthy control group on obsessive-compulsive traits. As was hypothesized, the schizophrenia relative group showed deficits in cognitive functioning in all three domains when compared to healthy controls. The bipolar I relative group did not show impairments in cognitive functioning that were to a lesser extent than the schizophrenia relative group (which was contrary to hypotheses). Rather, deficits were similar to the schizophrenia-relative group or no impairment was observed along cognitive domains for the bipolar relative group. Both discriminant function analyses and logistic regression analyses were utilized to develop prediction models for group membership. Relative type was best predicted by the variables of WMS-III Spatial Span (a measure of spatial working memory) and obsessive-compulsive traits. Results of the present study underscore the use of dimensional models in personality conceptualization and provide further evidence in supporting subtle differences in both personality and cognitive functioning between family members of patients diagnosed with the major mental illnesses. Treatment implications are discussed in the context of assisting the family unit in the treatment of schizophrenia and bipolar I disorder.