Attention-deficit/hyperactivity disorder (ADHD) is a common neurodevelopmental disorder often distinguished by the individual’s inattentive, hyperactive and impulsive behaviors.

With the advances in brain imaging technology, research shows that there are structural and functional brain differences between individuals diagnosed with and without ADHD. Specifically, previous studies have found that adults with ADHD have thinner cerebral cortical regions of the brain which are important for cognitive control and attention.

In 2013, Dr. Shaw and colleagues examined the developmental trajectories of the cerebral cortex from childhood into adulthood for people with ADHD. The researchers also linked these developmental brain trajectories to the clinical assessments of ADHD in adulthood.

With a longitudinal design, the researchers analysed 92 people with ADHD who also had childhood and adult clinical assessments with repeated neuroanatomic magnetic resonance imaging (MRI).

Dr. Shaw and colleagues found that ADHD persisted in 40% of 92 participants and that the severity of the adult ADHD symptoms were significantly associated with the cortical trajectories.

Specifically, when the number of adult ADHD symptoms increased, particularly inattentive symptoms, the rate of cortical thinning in the medial and dorsolateral prefrontal cortex also increased. The medial and dorsolateral prefrontal cortex are important regions for executive function, goal directed behavior, cognitive control and attention.

Analysing developmental trajectories also showed that cortical thickening or minimal thinning only occurred among remitted individuals. Remitted individuals were those whose symptoms decreased by adulthood to a level below the threshold for ADHD diagnosis.

Dr. Shaw and colleagues revealed that remitted ADHD adults tended to converge toward typical dimensions, in terms of structural and functional normalization of the cortex. However, persistent ADHD adults tended to show more fixed and non-progressive deficit.

Results from this study show that adult ADHD severity is associated with developmental trajectories of cerebral cortical regions of the brain that are integral for executive functions, cognitive control and attention. These findings also better enable our understanding of the developmental pathways to adult ADHD.