Identification and treatment issues surrounding attention deficit hyperactivity disorder (ADHD) are challenging enough. Now research is shedding light on long-term outcomes for people with ADHD. A May 20 study in Pediatrics reports that men who had ADHD in childhood are twice as likely to be obese in middle age, even if they no longer exhibit symptoms of the disorder.
ADHD is a mental disorder characterized by hyperactivity, impulsivity, inattention and inability to focus. It affects approximately 6.8 percent of U.S. children ages three to 17 in any given year, according to a recent report by the U.S. Centers for Disease Control. Medications used to treat ADHD, such as Ritalin (methylphenidate) or Adderall (dextroamphetamine and amphetamine), are stimulants that can suppress appetite. Two recent retrospective studies, however, have pointed to a possible increased risk for obesity among adults diagnosed with ADHD as children.
The new 33-year prospective study started with 207 healthy middle-class white boys from New York City between six and 12 years old, who had been diagnosed with ADHD. When the cohort reached an average age of 18, another 178 healthy boys without ADHD were recruited for comparison. At the most recent follow-up when the participants were an average age of 41, a total of 222 men remained in the study.
A troubling pattern emerged: A comparison of the men’s self-reported height and weight revealed obesity in twice as many men who had childhood ADHD were obese as in those without the disorder. The average body mass index (BMI) of the men with childhood ADHD was 30.1, and 41.4 percent were obese whereas those without the condition as kids reported an average BMI of 27.6 and an obesity rate of 21.6 percent. The association held even after the researchers controlled for socioeconomic status, depression, anxiety and substance abuse disorders.
The results have implications for parents currently raising kids with ADHD. “Many parents are concerned that their children may not be gaining as much weight as they should because [ADHD] medications can decrease appetite in the short run, but these results would lead me to be much less worried about that now,” says corresponding author F. Xavier Castellanos of the Phyllis Green and Randolph Cowen Institute of Pediatric Neuroscience at New York University Langone Medical Center. “It helps us to realize that over the long run, the potential risks of obesity, of overeating and of dysregulation, are a more prominent long-term concern."
The study is case-controlled, which means researchers identified participants (cases) with the condition and then matched them to a control population to compare outcomes and look for risk factor differences. Therefore, it cannot prove causation because it’s observational. Only a randomized, controlled trial could show that obesity is caused by ADHD—but it’s impossible to randomize participants to have ADHD, both because it is unethical and researchers do not know precisely what brings about the condition. Possible causes could include genetics, nutrition, environmental factors or brain injuries.
Despite these shortcomings, the study’s findings are similar to results in other research that has found links between ADHD and obesity. The previous studies, however, were retrospective (relying on participants’ recall), did not focus exclusively on ADHD (included other conduct disorders) or compared only men suffering from adult ADHD with those having remitted childhood ADHD, rather than to controls without ADHD. This prospective study is the most long-term and the first to focus exclusively on adult obesity rates in men with childhood ADHD compared with those who did not have the condition as children. Its findings therefore contribute to the growing evidence base for an association between obesity and childhood ADHD.