Objective measurement of physical activity in adults with ADHD and association with treatment outcome in a randomized controlled trial with a synbiotic intervention

Background ADHD is a neurodevelopmental disorder often persisting into adulthood. While Physical Activity (PA) is associated with improved ADHD symptoms in children, its effects in adults remain unclear. Emerging evidence suggests moderate PA enhances cognitive and behavioral functioning, though objective measurements are limited. Additionally, synbiotic interventions show potential in reducing ADHD symptoms, but possible synergies between PA and synbiotics are unexplored. Objective This study examines the relationship between objectively measured PA, ADHD diagnosis and severity in adults and assess whether PA influences synbiotic intervention effectiveness. Methods This is a secondary analysis of a subsample of the PROBIA trial (79 participants with ADHD, double-blind, randomized, controlled trial assessing a 10-week synbiotic intervention) and APPetite study (76 healthy controls). Forty participants in PROBIA received the synbiotic, 39 the placebo. PA was objectively measured via sensors tracking overall acceleration, Total Energy Expenditure (TEE), and moderate minutes of PA (MPA). Linear models, correlations, ANCOVAs, and regression analyses were used to examine associations between PA, ADHD symptoms, and treatment response to the synbiotic. Results PA did not significantly differ between the adult ADHD and control groups and was not correlated with ADHD symptom severity. PA did not predict symptom improvements, nor did it moderate the synbiotic effect. Conclusions PA seems similar in adults with ADHD and controls, and does not directly correlate with ADHD severity or specific symptoms. PA also did not moderate the effect of the symbiotic intervention. Further research needs to explore underlying mechanisms.