Does dopaminergic reward system contribute to explaining comorbidity obesity and ADHD?

Some recent studies have reported a strong link between obesity and attention-deficit/hyperactivity disorder (ADHD). However, to date, the factors underlying this newly described comorbidity are still unclear and unexplored. In the present article, we proposed that the dopamine system and implicate dopamine genes contribute to explaining the association between ADHD and obesity. The background for this hypothesis comes from studies on the association between ADHD and dopamine, as well as from investigations on dopamine in obese individuals. There is strong evidence that indicate catecholamines dopamine is very important in the pathophysiology of ADHD, as well as in the mechanism of therapeutic action of stimulant drugs. Furthermore, increasing evidence indicated that dopaminergic reward system is significantly associated with obesity. With regard to the therapeutic implications, recent studies indicate that methylphenidate (MPH) - a drug widely used for ADHD reduced overall energy intake with a selective reduction in dietary fat. Findings are consistent with a reward deficiency model of obesity whereby low brain dopamine predicts overeating and obesity, and administering agents that increase dopamine results in reduced feeding behavior. Given the above background, we hypothesize that the increased prevalence of ADHD in obese individual could be explained by the imbalance of dopaminergic reward system.