In 1989, the Child Psychiatry branch at the NIMH initiated a large scale longitudinal study of typical brain development, which to date has acquired data regarding brain development and function from over 1000 typically developing children (including twins and siblings) scanned from 1-7 times at approximately two year intervals. A study of a subset of these data, which included 829 scans from 387 unrelated individuals (age range 3-27, 209 males), demonstrated that neurodevelopmental trajectories were significantly different between males and females (Lenroot et al., 2007). Total brain size followed an inverted U trajectory in both sexes, with peak total brain size occurring at approximately 10.5 years in females and 14.5 years in males. Regional GM volumes also followed an inverted U shaped maturational curve and peaked earlier in females {SEE FIGURE 1}.
