A systematic review of neuroimaging studies of adults aged 35 and older with clinical, symptomatic and genetic risk for attention-deficit/hyperactivity disorder
TL;DR
Overall, ADHD-associated neurobiological alterations appear to persist into older age, and there were interactions between genetic risk for ADHD and Alzheimer’s disease-related pathology affecting brain and cognitive outcomes.
Abstract
Abstract Attention-deficit/hyperactivity disorder (ADHD) affects 2.5% of adults and is associated with cognitive decline and dementia. The neurobiological mechanisms contributing to adverse outcomes in ADHD are poorly understood. ADHD-related brain alterations may persist into later life and interact with ageing-related processes, potentially increasing susceptibility to neuropathology. This preregistered systematic review synthesised neuroimaging findings in adults aged 35 years and older with clinical, symptomatic, or genetic risk for ADHD, and summarised cognitive and clinical correlates. A search of five databases produced 13 included studies. Risk of bias was assessed using the Newcastle-Ottawa Scale. Most studies (11/13) had low risk of bias. Compared to controls, ADHD groups exhibited alterations in fronto-striatal, fronto-parietal, and limbic systems implicated in executive control and attention. Middle-aged adults with clinical ADHD showed more widespread cortical structural differences, whereas older adults demonstrated abnormalities primarily in frontal regions, possibly reflecting attenuation of differences through ageing. Two functional studies in those with clinical ADHD reported frontal hypoactivation alongside parietal hyperactivation, consistent with compensatory recruitment. Among undiagnosed samples, there were interactions between genetic risk for ADHD and Alzheimer’s disease-related pathology affecting brain and cognitive outcomes. Overall, ADHD-associated neurobiological alterations appear to persist into older age. Longitudinal investigations are needed to clarify these relationships.