Because of the wide range of clinical outcomes seen in ADHD, longitudinal studies have been of particular interest. Such studies indicate a developmental delay of cortical thickness trajectories most markedly for the frontal lobes (Shaw et al., 2007a) (see Figure 3). The general pattern of primary sensory areas attaining peak cortical thickness before polymodal, high-order association areas occurred in both those with and without ADHD. However, the median age by which 50% of the cortical points attained peak thickness was 10.5 years for ADHD and 7.5 years for controls. The area with the greatest age difference was the middle prefrontal cortex, reaching peak thickness at 10.9 years in those with ADHD and 5.9 years for controls.
