How Structural Changes Can Signal Brains of Young Adults With ADHD

Jaime Rosenberg

October is ADHD Awareness Month, and the 2017 theme is “Knowing is Better: ADHD Across the Life Span.” That has brought attention to the need for biomarkers to distinguish what physical traits can help identify those with attention-deficit/hyperactivity disorder. 

A study published earlier this year has received notice for being the first to uncover the macro- and microstructural changes in the brains of young adults with ADHD.
 
ADHD is one of the most frequently diagnosed neurodevelopmental disorders, and it is estimated that 65% of children with ADHD continue to have problems into adulthood.
 
“While ADHD is well-characterized at the behavioral level in children, little is known about the association between brain structure and ADHD diagnosis as well as symptoms across the lifespan,” the authors wrote.
 
The study, published in PLoS ONE, analyzed 72 young adults. Of the participants, there were 31 with ADHD and 41 controls without ADHD. Each individual was assessed according to the Diagnostic Statistical Manual of Mental Disorders-IV  (Text Revision) (DSM-IV-TR) criteria with the Structured Clinical Interview for DSM-IV and the QUEST method. The severity of the symptoms was evaluated using the Assessment of Hyperactivity and Attention (AHA), an 18-item questionnaire, based on DSM-IV criteria.
 
Magnetic resonance imaging (MRI) was used to capture T1 and diffusion tensor images (DTI). T1 images were used to assess brain macrostructure, such as the volume and structure of white matter and grey matter. DTI images were used to assess the brain microstructure and provide information about the mobility of water molecules in the white matter.
 
An ADHD diagnosis was associated with different grey and white matter concentrations as well as shape differences. No association was seen between brain macrostructure and ADHD symptoms, but ADHD symptoms were associated with microstructural findings, which were more prominent in childhood total symptoms than adult total symptoms.
 
T1 findings revealed that ADHD diagnosis for young adults was associated with decreased grey matter concentration, increased white matter concentration, and decreased shape in widespread areas involving frontal, temporal, striatal, pariental, and limbic regions. The incomplete maturations in structures support previous findings on cerebral and cerebellar volumetric reductions being associated with ADHD in children and adolescents. This also suggests that many of the brain areas associated with an ADHD diagnosis in childhood continue to be affected in young adulthood.
 
DTI findings verify that the abnormal cortico-cortical connectivity that develops early persists into young adulthood. Results also showed reduced fractional anisotropy (FA) – the directionality of water diffusion perpendicular to white matter fibers – and reduced mean diffusivity (MD) – overall water mobility – in the corpus callosum. The corpus callosum is central for communication between different brain areas. Reduced white matter density in the corpus callosum contributes significantly to brain network disturbances associated with ADHD. In addition, the dorsal striatum, in particular the putamen, showed regions with reduced FA on the right ride and increased radial diffusivity (RD) and MD on both sides. The dorsal striatum mediates aspects of decision-making, including predicting consequences of goal-directed actions, which are impaired in individuals with ADHD.
 
This study’s findings showed that an adult ADHD diagnosis and particular child symptoms were associated with widespread macro- and micro-structural changes in the frontal, basal ganglia, anterior cingulate, temporal, and occipito-parietal regions in young adults with ADHD. Associations between brain structure and ADHD symptoms in childhood were more prominent and widespread than in adults.
 
“The overall morphometric findings predict the ADHD diagnosis in 83% of cases, which demonstrates sufficient sensitivity to aid in the clinical assessment and potential as a biomarker for ADHD in young adults,” concluded the authors. 

Reference

Gehricke JG, Kruggel F, Thampipop T, et al. The brain anatomy of attention-deficit/hyperactivity disorder in young adults—a magnetic resonance imaging study [published online April 13, 2017]. PLoS ONE. https://doi.org/10.1371/journal.pone.0175433.
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