Obsessive-compulsive disorder (OCD) is a neuropsychiatric disorder characterized by obsessions and/or compulsions that are distressing, time consuming or significantly impairing. Obsessive-Compulsive Disorder (OCD) is the fourth most common psychiatric illness with a lifetime prevalence of 1–3%, and the World Health Organization (WHO) in 2006 identified OCD as a leading global cause of non-fatal illness burden. At this point, with recent mega-analyses of pooled neuroimaging data in OCD (e.g. 1), it is timely to consider what has been learned so far, the costs of this incremental knowledge, and future research targets for the field.