gray matter volume and hippocampal abnormalities in first-degree relatives of individuals with schizophrenia (Boos, Aleman, Cahn, Pol, & Kahn, 2007). The scope of the conclusions was limited, however, by the few brain structures in which enough data was available for adequate analysis. The findings were also criticized on the basis that the available twin data suggest the heritability of the hippocampus is relatively low (McDonald, Dineen, & Hallahan, 2008), highlighting the need to establish the heritability of a trait being considered as an endophenotype.
