Attention deficit hyperactivity disorder (ADHD) is the most common behavioral disorder in children, affecting three to five percent of that age group, according to the National Institutes of Health (NIH). ADHD results in problems with inattention, hyperactivity and impulsiveness, which can affect social interactions, work or school productivity and self-esteem. Research suggests that attention deficit disorder may be linked with another rising childhood disorder — obesity.
Obesity — an excessive amount of body fat — can lead to serious health problems, such as high blood pressure. In its most recent update, the American Heart Foundation found that 23.4 million children between the ages of 2 and 19 are overweight or obese. Of those 23.4 million children, 12.3 million are male and 11.1 million are female. The American Heart Foundation adds that 12 million of those children are considered obese; 6.4 million are males and 5.6 million are females. The NIH adds that “over the last two decades, this number [of overweight children] has increased by more than 50 percent and the number of ‘extremely’ overweight children has nearly doubled.”
Pagoto et al. (2009) found that children who have ADHD symptoms into adulthood have higher overweight and obesity rates that patients who only had ADHD symptoms during childhood. The study defined normal weight as a body mass index (BMI) of 24.9 kg/m2 and under; overweight as a BMI between 25.0 kg/m2 and 30.0 kg/m2; and obese as a BMI of 30.0 kg/m2 and greater. In patients who had ADHD only during childhood, 42.4 percent had a normal weight, 33.9 percent were overweight and 23.7 percent were obese. In patients who were diagnosed as children and continued to have symptoms into adulthood, 36.8 percent had a normal weight, 33.9 percent were overweight and 29.4 were obese.
Dopamine Link to ADHD and Obesity
Different studies have hypothesized about the link between obesity and ADHD. One hypothesis is that dopamine comes into play in both conditions, thus linking them together. Researchers Benjamin Charles Campbell and Dan Eisenberg (2007) note that dopamine levels in the brain increase when food is present, even if the person does not eat it. Dopamine is linked to the reward system, causing a person to feel happy when there is an increase in levels. By activating the dopaminergic pathways, eating becomes a pleasurable task.
Those with attention deficit disorder, in turn, have lower dopamine levels, particularly in the prefrontal cortex. Dopamine levels affect working memory, resulting in problems sustaining attention during a task. The authors note that “this switch in attention may be associated with a phasic increase in dopamine reinforcing the reward from novelty.” Thus, any action that increases the dopamine levels, such as eating, will be appealing for those with ADHD. The authors add that certain factors with ADHD can prevent the patient from only eating until full. For example, the poor inhibition control can contribute to overeating. Because of the satisfaction that comes from eating, those with ADHD may use food to self-medicate and increase dopamine levels. The overeating can lead to obesity if not monitored.
Obesity Risk with ADHD Medication
Treating ADHD without medication also may contribute to overweight in children. Waring and Lapane (2008) found that those with ADHD who do not use medications are 1.5 times more likely to be overweight than those with ADHD who take medications for the disorder. The study, which interviewed 5,680 children with ADHD, found that only 57.2 percent of those with ADHD took medications. The authors note that those who take attention deficit disorder medication are 1.6 times more likely to be underweight than those who do not take medication. This trend may be due to the side effects of stimulants, which the NIH states are the primary drug for ADHD. These side effects include weight loss and a reduced appetite.
Waring and Lapane’s results correspond to the dopaminergic pathway findings. If those with ADHD tend to overeat, the side effects of the stimulants would discourage that. Another factor is the mechanism of the drug. The National Institute on Drug Abuse (NIDA) states that stimulants, like amphetamines and methylphenidate, increase dopamine levels in the brain, thus reducing ADHD symptoms. Therefore, if dopamine levels are not managed, those with ADHD may overeat to increase satisfaction levels, which can lead to obesity.
Charles, Benjamin C. and Dan Eisenberg. Obesity, Attention Deficit-Hyperactivity Disorder and the Dopaminergic Reward System. Collegium Antropologicum, March 2007 (PDF).
Pagoto, Sherry L. et al. Association Between Adult Attention Deficit/Hyperactivity Disorder and Obesity in the US Population (PDF). Epidemiology, March 2009.
Waring, Molly E. and Kate L. LaPane. Overweight in Children and Adolescents in Relation to Attention-Deficit/Hyperactivity Disorder: Results From a National Sample. Pediatrics, Vol. 122, No. 1: July 2008.