Abstract
Attention-Deficit/Hyperactivity Disorder (ADHD) is the most common neurodevelopmental disorder diagnosed in children. Questions regarding its increased diagnostic rates and pharmacological treatments in developing children have led to a more holistic review of the multi-system pathophysiology observed in ADHD. The dopaminergic neurotransmitter system, known for its influence on reward-motivated behaviors and motor control, and the frontostriatal systems, that mediate motor, cognition, and behavior, are associated with ADHD’s development. However, studies have shown that these neural systems do not wholly account for ADHD’s multilayered and heterogeneous symptom presentation. For instance, the literature suggests that emotional dysregulation, the inability to regulate one’s emotional responses to provoking stimuli, is associated with increased risk for social impairment in ADHD. A broader examination of physiological systems in children with ADHD has found potential markers in the heart-brain and gut-brain axes that correspond with certain behaviors associated with emotional dysregulation in recent studies. Hence, the purpose of this meta-analysis is to aggregate ten applicable published case studies and analyze task-related heart rate reactivity (HRR; n = 5 studies) and gut microbiota (n = 5 studies) data in children with and without ADHD. Data from a total of 531 youth with ADHD and 603 youth without ADHD revealed significant small and medium effect sizes for higher Chao1 levels and Actinobacteria levels in the ADHD group, respectively, but no evidence of altered task-related HRR. Thus, further research into multi-system psychophysiological measures of emotional dysregulation and ADHD is warranted. The clinical, empirical, and educational implications of these findings are discussed.Systematic Review Registration https://www.crd.york.ac.uk/prospero/, identifier PROSPERO (CRD42021236819).
Highlights
Attention-Deficit/Hyperactivity Disorder (ADHD) is one of the most commonly diagnosed childhood neurodevelopmental disorders [1], with an estimated lifetime prevalence rate of 9.4% in the United States [2] and 7.2% worldwide [1, 3]
We examined the evidence for two physiological systems implicated in cognitive and emotional dysregulation: heart rate reactivity and gut microbiota
2.2.1 Task-Related Heart Rate Reactivity Required Data for Analysis Consistent with methods used across heart rate reactivity (HRR) studies, HRR to laboratory tasks was calculated using the difference in average bpm between the task and baseline phases [28]
Summary
Attention-Deficit/Hyperactivity Disorder (ADHD) is one of the most commonly diagnosed childhood neurodevelopmental disorders [1], with an estimated lifetime prevalence rate of 9.4% in the United States [2] and 7.2% worldwide [1, 3]. Youth with ADHD are more likely than their neurotypical counterparts to experience adverse symptoms and outcomes such as lower academic attainment, impaired psychosocial functioning [4], increased substance use [5], and reduced occupational success in adulthood [6]. With this growing prevalence, direct health care expenditures and associated indirect costs have increased [7]; the resulting annual societal costs (e.g., medical care, caregiver strain, education, reduced work productivity) accompanying childhood ADHD in the U.S are estimated to be $124.5 billion [8]. This study aims to review recent evidence for the cardiovascular and gastrointestinal microbiome underpinnings of emotional dysregulation in children with ADHD, discuss implications and provide recommendations for treatment and future research
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