In summary, clinical studies indicate diagnosis-specific group anatomic brain differences that although not diagnostic are beginning to elucidate the timing and nature of deviations from typical development. Using trajectories (i.e., morphometric measures by age) as an endophenotype may provide discriminating power where static measures do not (Giedd et al., 2008). It is increasingly clear that the same molecular genetic risk can be associated with a range of psychiatric phenotypes, including autism, bipolar disorder, schizophrenia, mental retardation, and epilepsy. Conversely, the same psychiatric phenotype is likely to reflect numerous individually rare genetic abnormalities such as copy number variants (Bassett et al., 2010; McClellan and King, 2010). Exploring the role of genetic variants on timing of brain development may clarify some of these issues of sensitivity and specificity.
