Emerging evidence suggests that SG differences in brain morphometry emerge in childhood and continue to differentiate in adolescence and adulthood (Giedd, Raznahan, Mills, & Lenroot, 2012; Lenroot et al., 2007; Luders, Gaser, Narr, & Toga, 2009). At baseline, boys have larger total brain size (by ~8-10%) than girls (Giedd et al., 2012; Lenroot et al., 2007). Structural differences in boys and girls have been found in caudate, amygdala, and hippocampus (Giedd et al., 2012) – all regions implicated in addiction. Cortical and subcortical gray matter volumes generally follow an inverted U-shaped trajectory, with adolescent females peaking earlier than males (Giedd et al., 2012; Lenroot et al., 2007). Through adolescence, males tend to have a steeper rate of increase in white matter volume compared to females (Lenroot et al., 2007). In adulthood, in studies where brain size is controlled, women have more regional gray matter concentration than men (Luders et al., 2009).
