The cortical analyses showed that pediatric/adolescent OCD patients (n = 407) versus healthy control children/adolescents (n = 324) have thinner left and right inferior parietal, left superior parietal and lateral occipital cortices (Cohen's d values between −0.24 and − 0.31). Adult OCD patients (n = = 1,498), in comparison to adult healthy controls (n = 1,436), showed a lower surface area of the transverse temporal cortex (Cohen's d = −0.16) and a thinner bilateral inferior parietal cortex (Cohen's d = −0.14; Boedhoe et al., 2018). The involvement of the parietal cortex is consistent with the vertex‐wise FreeSurfer findings of the OBIC consortium (Fouche et al., 2017), and the effect was now further found to extend to children, suggesting altered maturation of the parietal cortex early in life that persists into adulthood. One obvious discrepancy with previous meta‐ and mega‐analysis of structural MRI in OCD is the lack of involvement of the prefrontal regions; this may reflect differences in methods used: The atlas‐based approach to cortical thickness and surface areas that has been used in ENIGMA (segmenting whole structures using coarse
