Structural neuroimaging studies suggest the presence of subtle abnormalities in the brains of patients with bipolar disorder. The influence of genetic and/or environmental factors on these brain abnormalities was unknown. We investigated the contribution of genetic and environmental factorsonbrain volume in bipolar disorder. Magnetic resonance imaging (1.5 T) brain scans of monozygotic (MZ) or dizygotic (DZ) twins concordant and discordant for bipolar disorder were compared with healthy twin pairs. Decreases in white matter were related to the genetic risk of developing bipolar disorder (bivariate heritability,77%; 95% confidence interval, 38% to 100%). Significant environmental correlations were found for cortical gray matter. These relationships all became more pronounced when data were corrected for lithium use. Focusing on genes controlling white matter integrity may be a fruitful strategy in the quest to discover genes implicated in bipolar disorder. Elucidating the mechanism by which lithium attenuates brain matter loss may lead to the development of neuroprotective drugs. (Van der Schot et al, Arch Gen Psychiatry. 2009;66(2):142-151).

To investigate whether these changes are progressive, we are currently rescanning these participants.