Abstract
Attention Deficit Hyperactivity Disorder (ADHD) is a neurodevelopmental disorder with a complex symptomatology, and core symptoms as well as functional impairment often persist into adulthood. Recent investigations estimate the worldwide prevalence of ADHD in children and adolescents to be ~7%, which is a substantial increase compared to a decade ago. Conventional treatment most often includes pharmacotherapy with central nervous stimulants, but the number of non-responders and adverse effects call for treatment alternatives. Exercise has been suggested as a safe and low-cost adjunctive therapy for ADHD and is reported to be accompanied by positive effects on several aspects of cognitive functions in the general child population. Here we review existing evidence that exercise affects cognitive functions in children with and without ADHD and present likely neurophysiological mechanisms of action. We find well-described associations between physical activity and ADHD, as well as causal evidence in the form of small to moderate beneficial effects following acute aerobic exercise on executive functions in children with ADHD. Despite large heterogeneity, meta-analyses find small positive effects of exercise in population-based control (PBC) children, and our extracted effect sizes from long-term interventions suggest consistent positive effects in children and adolescents with ADHD. Paucity of studies probing the effect of different exercise parameters impedes finite conclusions in this regard. Large-scale clinical trials with appropriately timed exercise are needed. In summary, the existing preliminary evidence suggests that exercise can improve cognitive performance intimately linked to ADHD presentations in children with and without an ADHD diagnosis. Based on the findings from both PBC and ADHD children, we cautiously provide recommendations for parameters of exercise.
Highlights
Based on the aforementioned notion that Attention Deficit Hyperactivity Disorder (ADHD) represents the extremes of traits present throughout the general population, the results suggest that children with ADHD are likely to benefit the most from acute exercise
As the ADHD affected networks and cerebral structures described above entail multiple monoaminoceptive regions [231,232], it is tempting to speculate that dysfunctional regulation of monoamines and monoaminergic signaling may represent a biochemical underpinning of the reported ADHD related patterns of brain activity
It is positive that the present review found consistent and large positive effects for long-term exercise interventions and it could be hypothesized that long-term changes in performance in e.g., tests of executive functions (EF) in children and adolescents with and without ADHD may relate to accompanying exercise-induced structural adaptations
Summary
ADHD is in general associated with lower performance, neuropsychological tests are in isolation unlikely to have sufficient selectivity necessary to entail clinical value [32]. Deploying a comprehensive test-battery including several tests within each EF domain can increase sensitivity and specificity to 89 and 80% respectively [41] Another important point of criticism is the practice of comparing pooled average performance scores with little attention to intra-individual variability. Exemplified; The lower selective and sustained attention ability associated with ADHD results in lower average performance (e.g., higher mean reaction times (RT) in a flanker test), which originates in part from large intra-individual variability [42,43,44]. This variability does not stem from large systematic fluctuation in trial-to-trial performance, but rather from few very high RTs, signifying lapses in attention [45]. We provide a comprehensive overview of the effect of exercise on tests of NCFs where children with ADHD generally display subpar performance
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