Effect of ADHD Course and Onset on Brain Outcomes
The purpose of this study was to examine the effects of ADHD course and age of onset on brain outcomes. Adult-onset ADHD is a recent development in the field, and whether brain deviations found in childhood-onset ADHD are also found for adult-onset ADHD has not yet been examined. The four groups we examined were childhood-onset remitted, childhood-onset persistent, adult-onset, and no ADHD. Our a priori regions of interest were: (1) hippocampus (involved in memory and spatial navigation), (2) amygdala (involved in emotional processing), (3) prefrontal cortex (involved in executive function), and (4) cerebellum (involved in planning and executing movements). Participants were from a twin cohort in the Minnesota Twin Family Study (MTFS) and the sample was enriched for externalizing psychopathology, including ADHD, at age 11. MRI measures were taken at age 24. Results were obtained by comparing the cortical thickness and subcortical volumes of these regions in the three ADHD groups to the no ADHD control group. Statistical analyses showed that the cerebellum in childhood-onset persistent ADHD was significantly smaller than the cerebellum of individuals in the control group. Results also showed that the amygdala in the adult-onset group was significantly smaller than the amygdala of individuals in the control group. The regions containing these differences (cerebellum and amygdala) are the same as those implicated in commonly comorbid adult disorders, such as depression and anxiety, and future studies should account for these comorbidities in their analyses.