Given that nearly all neuropsychiatric disorders have different prevalence, age of onset, and symptomatology between males and females, sex differences in typical developmental brain trajectories are highly relevant for studies of pathology. Robust sex differences in developmental trajectories are noted for nearly all structures, with GM volume peaks generally occurring 1–3 years earlier in females (Lenroot et al., 2007). To assess the relative contributions of sex chromosomes and hormones, our group is studying subjects with anomalous sex chromosome variations (e.g., XXY, XXX, XXXY, XYY) (Giedd et al., 2007), as well as subjects with anomalous hormone levels (e.g., congenital adrenal hyperplasia, familial male precocious puberty, Cushing syndrome) (Merke et al., 2003, 2005).
