In the subcortical analyses, we found clear differences between the pediatric OCD patients (compared with healthy controls, n = 335 and 287, respectively) and the adult OCD patients (compared with healthy controls, n = 1,495 and 1,472, respectively) (Boedhoe et al., 2017). Pediatric OCD was associated with greater volume of the thalamus (Cohen's d = 0.38), but this effect was only detectable in the comparison of unmedicated OCD versus healthy controls. We recently replicated this finding with data from the Generation R cohort (Jaddoe et al., 2010), in which children with probable OCD (scoring above the cut‐off on the short OCD screener) also had a larger thalamus, on average (unpublished data). This may suggest altered neurodevelopment in children prone to develop OCD. Nevertheless, the thalamus is not a uniform structure but rather consists of multiple subnuclei, each with its own cortical connectivity profile and functions (Behrens et al., 2003). OCD‐related enlargement of the overall thalamus may therefore be driven by one or a few subnuclei. Which subnuclei drive this effect is currently unknown, although shape analysis has revealed increased surface
