Resting-state functional connectivity alterations in adult ADHD: A systematic review of rs-fMRI studies

Attention-Deficit/Hyperactivity Disorder (ADHD) often persists into adulthood and causes significant functional impairments. Resting-state functional MRI (rs-fMRI) offers valuable insights into intrinsic brain connectivity; however, connectivity (FC) alterations specific to adults with ADHD remain unclear. This systematic review aimed to synthesize rs-fMRI studies comparing adults with ADHD and healthy controls, identify consistent FC patterns, and assess methodological quality.

Following PRISMA guidelines, PubMed, Embase, and Scopus were searched for rs-fMRI studies involving adults diagnosed with ADHD per DSM-IV/DSM-5 criteria. Eligible studies examined FC differences between adults with ADHD and healthy controls. Data extraction included study characteristics, imaging parameters, and FC methodologies. Study quality was assessed using the Newcastle-Ottawa Scale.

Eight studies (n = 529; 264 ADHD, 265 controls) met inclusion criteria. FC analyses employed Seed-Based Analysis (SBA), Independent Component Analysis (ICA), and graph theory methods. Despite methodological heterogeneity, consistent FC alterations were observed: increased FC in the default mode (DMN), visual (VN), and central executive (CEN) networks, and decreased FC in the ventral attention (VAN) and somatomotor (SMN) networks. Alterations were predominantly left-hemispheric.

Adults with ADHD exhibit distinct rs-FC disruptions, mainly involving DMN, VAN, CEN, and SMN. Standardized analytic approaches and subtype-specific analyses are needed for improved clinical relevance.