Diffusion tensor imaging white matter endophenotypes in patients with schizophrenia or psychotic bipolar disorder and their relatives

ObjectiveBoth schizophrenia and bipolar disorder are hypothesized to involve disordered brain connectivity. Prior studies show low white matter integrity, measured with diffusion tensor imaging, for both disorders. The authors studied disease specificity and endophenotypic status of these abnormalities by examining patients and their unaffected relatives.MethodThe 513 participants included probands with schizophrenia, probands with psychotic bipolar disorder, their first-degree relatives, and healthy comparison subjects. Fractional anisotropy measures of white matter integrity were collected at two sites as a part of the Bipolar-Schizophrenia Network on Intermediate Phenotypes project. Relatives with cluster A or B personality characteristics were further examined.ResultsBoth the probands with schizophrenia and those with psychotic bipolar disorder showed lower fractional anisotropy than the comparison subjects in multiple white matter regions; differences were more marked in schizophrenia. No significant...