Potential Genetic Intersections Between ADHD and Alzheimer’s Disease: A Systematic Review

Background: attention-deficit/hyperactivity disorder (ADHD) and Alzheimer’s disease (AD) are distinct neurological conditions that may share genetic and molecular underpinnings. ADHD, a neurodevelopmental disorder, affects approximately 5% of children and 3% of adults globally, while AD, a neurodegenerative disorder, is the leading cause of dementia in older adults. Emerging evidence suggests potential overlapping contributors, including pathways related to synaptic plasticity, neuroinflammation, and oxidative stress. Methods: this systematic review investigated potential genetic predispositions linking Attention-Deficit/Hyperactivity Disorder (ADHD) and Alzheimer’s Disease (AD). Following PRISMA guidelines, a search was conducted in Web of Science, Embase, PsycINFO, and PubMed using keywords related to ADHD, AD, and genetic factors. Studies included were original human studies utilizing genetic analyses and ADHD polygenic risk scores (PRS), with AD confirmed using established diagnostic criteria. Exclusion criteria comprised non-original studies, animal research, and articles not addressing genetic links between ADHD and AD. Screening was conducted with Rayyan software, assessing relevance based on titles, abstracts, and full texts. Results:. The search identified 1450 records, of which 1092 were screened after duplicates were removed. Following exclusions, two studies met inclusion criteria. One study analyzed ADHD-PRS in 212 cognitively unimpaired older adults using amyloid-beta (Aβ) PET imaging and tau biomarkers. The findings revealed that ADHD-PRS was associated with progressive cognitive decline, increased tau pathology, and frontoparietal atrophy in Aβ-positive individuals, suggesting that ADHD genetic liability may exacerbate AD pathology. Another study assessed ADHD-PRS in a cohort of 10,645 Swedish twins, examining its association with 16 somatic conditions. The results showed modest risk increases for cardiometabolic, autoimmune, and neurological conditions, with mediation effects through BMI, education, tobacco use, and alcohol misuse, but no direct link between ADHD-PRS and dementia. Discussion and conclusion: this review highlights preliminary but conflicting evidence for a genetic intersection between ADHD and AD. One study suggests that ADHD genetic liability may exacerbate AD-related pathology in Aβ-positive individuals, whereas another large registry-based study finds no direct link to dementia, with associations largely mediated by lifestyle factors. The potential ADHD–AD relationship is likely complex and context-dependent, influenced by biomarker status and environmental confounders. Longitudinal studies integrating genetics, biomarkers, and detailed lifestyle data are needed to clarify this relationship.