SA95. A Tale of 2 Endophenotypes in Clinically Unaffected Relatives of Schizophrenia Patients

Background: A number of traits associated with schizophrenia aggregate in relatives of schizophrenia patients at rates much higher than that of the clinical disorder. These traits, considered candidate endophenotypes, may be alternative, more penetrant manifestations of schizophrenia risk genes than schizophrenia itself. In order for an endophenotype to potentially increase the power of genetic analyses, not only should the distribution of the quantitative trait be heterogeneous in unaffected relatives, but the trait must also be found in unaffected relatives at a higher rate than in the general population. Methods: Here we evaluate the suitability of 2 provisionally identified endophenotypes: thought disorder with schizophrenic features and antisaccade error rate. Results: We demonstrate that thought disorder with schizophrenic features meets both of the criteria for an endophenotype. In contrast, we show that, while there is significant heterogeneity in performance on the antisaccade task in unaffected relatives, we do not find evidence of a higher rate of antisaccade errors in unaffected relatives compared to normal controls. Conclusion: These findings provide further support for the utility of this approach for evaluating the suitability of a given trait as a candidate endophenotype and suggest that thought disorder with schizophrenic features may be more useful as a schizophrenia endophenotype than antisaccade error rate.