Exercise as a Complementary Intervention for Adults with Attention Deficit Hyperactivity Disorder: A Neurobiological Analysis

Objective: Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterized by persistent inattention and/or hyperactivity-impulsivity that interferes with functioning or development. Stimulant medication remains its first-line treatment, but perceived ineffectiveness, side effects, and lack of treatment access may pose challenges for adults with ADHD. Physical exercise has received increasing attention in the treatment of children with ADHD, but research in adults is scarce. This paper aims to explore possible mechanisms by which exercise could reduce inattentive, hyperactive, and impulsive symptoms in adults with ADHD. Methods: Respective narrative reviews were conducted on the neurobiology of exercise and of ADHD in adults using relevant search terms in PubMed. Findings were compared to formulate possible mechanisms by which exercise could improve ADHD symptoms in adults. Results: Exercise could reduce ADHD symptoms in adults via enhancement of neuroplasticity and structural integrity in relevant brain regions, improved functional connectivity in cognitive networks, modulation of neurotransmitter release and function, improved hypothalamic-pituitary-adrenal axis function, reduced oxidative stress and neuroinflammation, enhancement of reward and motivation circuitry, and beneficial epigenetic modifications. Limitations: This narrative review relied on a single database and single-author screening with date and language restrictions, and its conclusions are limited by heterogeneous, largely observational evidence, indirect mechanistic data from non-ADHD populations, and few intervention studies in adults with ADHD. Conclusions: Future research should attempt to confirm the efficacy of exercise in reducing ADHD symptoms in adults as well as the proposed mechanisms for such a relationship. Verification of these issues would open the door to an evidence-based, inexpensive, widely available, and broadly beneficial complementary intervention for adults with ADHD.