Does excessive daytime sleepiness contribute to explaining the association between obesity and ADHD symptoms?

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Summary

Recent studies suggest a significant association between obesity and attention-deficit/hyperactivity disorder (ADHD). The factors underlying this newly described comorbidity are still unclear and unexplored. In the present article, we propose that excessive daytime sleepiness (EDS) contributes to explaining the association between ADHD and obesity. The background for this hypothesis comes from studies on the association between ADHD and EDS, as well as from investigations on EDS in obese individuals. Available studies suggest that ADHD behaviours are significantly associated with EDS. Moreover, increasing evidence indicates that obesity is significantly associated with EDS independently of sleep-disordered breathing (SDB) or any other sleep disorders. Given the relationship between EDS and ADHD behaviors, we hypothesize that the higher than expected rates of EDS in obese individuals contribute to explaining the association between obesity and ADHD behaviors. We further speculate on the role of the brain derived neurotrophic factor (BDNF) and other molecules such as the proinflammatory cytokines IL-6 and TNF-α. Our hypothesis generates potentially relevant clinical and therapeutic implications. From a clinical standpoint, it may suggest to systematically look for ADHD symptoms (including hyperactivity and impulsivity) in obese patients described as sleepy. With regard to the therapeutic implications, we suggest that wake-promoting agents with anorexigenic effect, such as mazindol, might be particularly indicated for the treatment of ADHD symptoms in obese patients, since they might address both ADHD symptoms and weight reduction. In conclusion, considering the burden that ADHD adds to obesity, we believe that further studies on the comorbidity between obesity and ADHD are necessary. Research on the role of EDS might allow advancements in this field, suggesting a more effective management and, ultimately, a better quality of life of patients with both obesity and ADHD.

Introduction

Attention-deficit/hyperactivity disorder (ADHD) is one of the most common and impairing childhood psychiatric conditions, estimated to affect 5–10% of school-aged children [1]. According to the Diagnostic and Statistical Manual of Mental Disorders-4th edition (DSM-IV) [2], ADHD is characterized by pervasive and developmentally inappropriate symptoms of inattention and/or impulsivity-hyperactivity. Impairing symptoms of ADHD may persist into adulthood in up to 60% of cases [3]. ADHD is frequently associated with psychiatric and developmental disorders such as oppositional defiant disorder, conduct disorder, anxiety disorders, depressive disorders, speech and learning disorders [4], [5].

Although overlooked in the past, a significant association between ADHD/ADHD traits and obesity has been suggested by recent empirically based evidence, both from clinical [6], [7], [8], [9], [10], [11] and epidemiological studies [12], [13]. The factors underlying this newly described comorbidity are still unclear and unexplored. In a previous paper published in this Journal, Bazar et al. [14] suggested that an excess of exogenously supplied information predisposes to both obesity and ADHD. In the present article, we propose another hypothesis, i.e., that excessive daytime sleepiness (EDS) contributes to explaining the association between ADHD and obesity.

Section snippets

ADHD and EDS

In recent years there has been a growing interest in the relationship between EDS and ADHD behaviors. EDS has been assessed both with “subjective measures”, i.e., questionnaires on sleep and alertness, and “objective methods”, i.e., polysomnographic measures provided by the multiple sleep latency test (MSLT). (The MSLT consists of four or five 20–30 min nap opportunities given at 2 h intervals during the day; the basic parameters measured are latency to sleep onset and latency to rapid eye

The hypothesis

Given the association between EDS and ADHD behaviors, we hypothesize that the higher than expected rates of EDS in obese individuals contribute to explaining the comorbidity between obesity and ADHD traits (i.e., inattention, hyperactivity, and impulsivity). To our knowledge, currently, no studies have explored this hypothesis. Therefore, we believe that studies assessing the relationship between EDS and ADHD behaviours in obese subjects using both subjective and objective measures of EDS

Implications

Our hypothesis generates potentially relevant clinical and therapeutic implications for the management of ADHD and obesity when coexisting.

Conclusion

In light of the personal and social burden that comorbid ADHD adds to obesity and considering that the treatment of ADHD might actually improve the management of obesity itself, we think that further studies on this comorbidity are necessary. Research on the role of EDS might allow advancements in this field. Studies assessing the relationship between EDS (measured both with subjective and objective methods) and ADHD in obese subjects as well as investigations in the potential molecular

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