Neuroimaging in attention-deficit/hyperactivity disorder

Abstract

Purpose of review Neuroimaging research on attention-deficit/hyperactivity disorder (ADHD) continues growing in extent and complexity, although it has yet to become clinically meaningful. We review recent MRI research on ADHD, to identify robust findings, current trends and challenges. Recent findings We identified 40 publications between January 2019 and September 2020 reporting or reviewing MRI research on ADHD. Four meta-analyses have presented conflicting results regarding across-study convergence of functional and resting-state functional (fMRI and R-fMRI) studies on ADHD. On the other hand, the Enhancing NeuroImaging Genetics Through Meta-Analysis international consortium has identified statistically robust albeit small differences in structural brain cortical and subcortical indices in children with ADHD versus typically developing controls. Other international consortia are harnessing open-science efforts and multimodal data (imaging, genetics, phenotypic) to shed light on the complex interplay of genetics, environment, and development in the pathophysiology of ADHD. We note growing research in ‘prediction’ science, which applies machine-learning analysis to identify biomarkers of disease based on big data. Summary Neuroimaging in ADHD is still far from informing clinical practice. Current large-scale, multimodal, and open-science initiatives represent promising paths toward untangling the neurobiology of ADHD.

Cumulative Effects of Resting-state Connectivity Across All Brain Networks Significantly Correlate with ADHD Symptoms

“…Although these investigations have identified a variety of distinct and localized structural and functional brain features associated with ADHD (Albajara Sáenz, Villemonteix, and Massat 2019; Hoogman et al 2020; Mooney et al 2021), results have not yet yielded reliable replication. This is likely secondary to relatively small brain-behavior effect sizes (Pereira-Sanchez and Castellanos 2021; Feczko et al 2021; Marek et al 2020; Smith and Nichols 2018). Nonetheless, considerable evidence supports the proposal that biological and physiological correlates of ADHD are not simply localized alterations in brain function, but rather constitute widely distributed functional brain systems as evaluated by resting state functional connectivity MRI (rs-fcMRI) studies.…”

Differential structure-function network coupling in the inattentive and combined types of attention deficit hyperactivity disorder

“…Although SC-FC coupling in the DMN significantly differed between ADHD subtypes, the subnetworks seem to work together to manifest a different degree of inattentiveness and hyperactivity in the ADHD-I and ADHD-C groups. Given that structural differences between individuals with ADHD and controls has been demonstrated in children but not adults, further work on the SC-FC coupling should include longitudinal data [ 93 ]. These findings suggest that the structure-function network relationship may provide important neurobiological clues for understanding ADHD subtypes in children.…”

Resting-State fMRI to Identify the Brain Correlates of Treatment Response to Medications in Children and Adolescents With Attention-Deficit/Hyperactivity Disorder: Lessons From the CUNMET Study

“…The “Clínica Universidad de Navarra Metilfenidato” (CUNMET) study was designed as a proof-of-concept study in partial fulfillment of the requirements for a Ph.D. [see also ( 6 , 9 )]. The study was based at the child and adolescent psychiatry outpatient service at Clínica Universidad de Navarra, a tertiary university hospital in the north of Spain.…”

“…Another major limitation was the limited sample size, even if it was in line with that of most previous studies ( 9 ). Small sizes have been endemic in neuroimaging research of ADHD ( 6 , 8 ), and medication studies present further logistical complications for recruitment and retention of participants. This is partially offset by the within-subject analyses which increase statistical power relative to cross-sectional designs ( 29 ).…”

“…Neuroimaging research in mental disorders, including ADHD, aims to elucidate the pathophysiology and neuropsychopharmacology of these conditions and their treatments in a quest for personalized medicine ( 5 ). Yet, despite a growing literature and increasing methodological sophistication, neuroimaging is still unable to inform “bedside” clinical decisions ( 6 ).…”