Invisible populations: Who is missing from research in intellectual disability?

It is estimated that approximately 41% of adults with intellectual and developmental disability (IDD) are served through the developmental disabilities (DD) system in the US. The remaining 59% include individuals who meet diagnostic criteria but are not actively receiving paid services or may not be known to the DD system. Scholars have referred to this group as the "hidden majority." Very little is known about the health and well-being of these adults. It remains to be seen if the hidden majority is comparably susceptible to mental health difficulties, given how little is known about this population by DD systems. The purpose of this manuscript is to highlight where one may identify individuals belonging to this hidden population and how researchers might effectively recruit from this group so as to ensure more representative samples of all people with IDD.