The only case-control study of the effects of an additional Y chromosome on brain development is from neuroimaging data obtained on the subjects identified as part of the previously described Edinburgh cohort study [Warwick et al., 1999]. Ten 47,XYY males were included (mean age 21.8, SD 3.2 years). The subjects were significantly taller than the control subjects (188.2 cm, SD 4.7 vs. 183.2, SD 4.8, P < .005), and had significantly lower IQ (mean NART IQ 90.4, SD 9.3 vs. 105.1, SD 7.8, P < .001). The 47,XYY group scored significantly higher on the antisocial traits component of the SIS. Brain imaging results showed no significant differences in brain volumes between 47,XYY and controls, although white matter hyperintensities were found in one of the 47,XYY subjects and no controls. There was no correlation between behavioral or cognitive indices and brain size in the XYY group, although antisocial traits did have a negative correlation with brain size in the healthy male controls.
