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

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-alpha. 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.