Neurobiological and neuropsychological differences in autism and ADHD

Abstract

Autism spectrum disorder and attention-deficit/hyperactivity disorder share cognitive and behavioral features, yet their overlap does not imply identical neurobiology. This narrative review integrates a large structural neuroimaging investigation, a meta-analysis of task-based functional magnetic resonance imaging, and a review of cerebellar and neurocognitive functioning. The evidence indicates partly distinct cortical and functional patterns alongside shared difficulties involving executive functions and distributed brain networks. Cerebellar contributions extend beyond movement to cognitive and emotional processes, although causal pathways remain uncertain. Psychosocial stress is relevant to daily functioning and the interpretation of symptoms, but the reviewed evidence does not establish stress as the cause of observed brain differences. Diagnostic interpretation is further complicated by co-occurring conditions, developmental variation, and the underrepresentation of female participants and people with greater support needs. These findings support multidimensional assessment that connects developmental history, neuropsychological functioning, and environmental demands. Current group-level imaging results provide explanatory context rather than a validated diagnostic test for an individual.