Multiple conventional meta‐analyses of VBM studies of OCD were subsequently published (Radua & Mataix‐Cols, 2009; Radua, van den Heuvel, Surguladze, & Mataix‐Cols, 2010; Rotge et al., 2010; Peng et al., 2012), using statistical methods to aggregate information on effect sizes, standard errors, and confidence intervals from primary published studies, in order to estimate overall effect size. To meta‐analyze voxel‐based data, an often‐used approach is the signed differential mapping (SDM) method, developed by Radua (https://www.sdmproject.com). A meta‐analysis using this method showed that compared to healthy controls, OCD patients have, on average, lower volumes of the dorsomedial prefrontal cortex (dmPFC)/dorsal anterior cingulate cortex (dACC) and greater volume of the bilateral striatum (mainly anterior putamen, extending into the caudate nucleus) (Radua & Mataix‐Cols, 2009). In comparison to other anxiety disorders, smaller volume of the dmPFC/dACC was found across disorders, whereas OCD patients had greater pallidal volume than did patients with anxiety disorders (Radua et al., 2010). An even larger cross‐disorder meta‐analysis of brain volume across mental disorders, including 193 studies (15,892 subjects) in six diagnostic groups (schizophrenia, bipolar disorder, major depressive disorder, substance
