Are the relative roles of genetic and environmental influences on brain structure during childhood and adolescence static? A recent meta-analysis found that heritability increased for a range of cognitive and behavioral features, including IQ, externalizing behaviors, anxiety, and depressive symptoms, although not ADHD (Bergen, Gardner, & Kendler, 2007). The post-pubertal onset of schizophrenia has raised the question of whether its manifestation could be related to developmental changes in brain gene expression (Cannon et al., 2003). Studies directly studying developmental changes in gene expression in animal models have found marked changes during both pre- and postnatal development. An intriguing study by Stead and colleagues (2006) compared gene expression across different regions of the brain in mice at different developmental stages. They found that developmental stage explained more of the variance in gene expression of different regions than any other factor, speaking to the importance of considering developmental effects on gene expression. Similar data from human brain development has been relatively sparse, in part due to the rarity of appropriate postmortem tissue samples from healthy pediatric subjects. However, a gradually accumulating body
