In contrast to previous mega-analyses from the OBIC consortium, we did not find cortical thickness abnormalities in the OFC, ACC, or dmPFC. Six (i.e. the entire OBIC sample) out of our 38 data sets were identical to those included in the OBIC mega-analysis. Apart from a much larger sample size including samples from more different countries, no discrepancies between demographic and clinical characteristics could be found between this sample and the OBIC sample. Thus these inconsistencies are likely to reflect differences in analysis methods and the overall sample size. While FreeSurfer measures thickness and surface area separately, it segments whole structures based on probabilistic information from a predefined atlas (20), compared to VBM’s voxel-wise registration (26). Mainly global or regional differences in structure can be inferred from these atlas-based FreeSurfer analyses, as opposed to local morphology as with VBM. Moreover, the FreeSurfer mega-analysis of the OBIC consortium (12) was conducted using vertex-based analyses rather than the atlas-based approach we used in the current study. It is thus possible that certain abnormalities on vertex level are not detectable when averaging data
