Different cortical regions are highlighted by our statistical comparison of COS probands and HCs, than for SIBs and HCs. This is most notable in anterior cingulate, lateral temporal and parietal region. These differences could be due to several mechanisms. They could reflect factors operating in COS probands but not SIBs, such as; a greater burden of genetic or environmental risk for psychosis; the direct consequences of active psychosis on brain development; or medication treatment. Alternatively, differences between COS probands and their non-psychotic SIBs could reflect active compensatory processes in SIBs, or the “unmasking” in SIBs of primary psychosis risk correlates that are obscured by active disease in probands. A longitudinal discordant monozygotic twin study design could test these various accounts more clearly, although the necessarily limited sample size of such a study would complicate the modeling of anatomical change.
