Girls with attention-deficit/hyperactivity disorder (ADHD) were twice as likely as those without the condition to become obese by young adulthood, researchers reported in Mayo Clinic Proceedings.

There was a smaller and nonsignificant trend in the same direction for boys, said Seema Kumar, MD, of the Mayo Clinic in Rochester, Minn., and colleagues. "To our knowledge, this is the first longitudinal population-based study to examine the association between ADHD and development of obesity using patients with ADHD and controls of both sexes derived from the same birth cohort," Kumar and colleagues wrote.

The study's findings "highlight the need for monitoring of weight status of children with ADHD for overweight or obesity and need for obesity prevention efforts via healthy lifestyle (dietary and physical activity related) within the home as well as in schools and medical staff for children with ADHD," the researchers said. The study included 5,718 children born from 1976 to 1982 in one Minnesota school district. They were followed into their mid-20s. The investigators used school and medical records to determine diagnoses of ADHD. Each participant with ADHD was randomly assigned two age- and sex-matched controls without ADHD from the cohort. Height and weight measurements were obtained from medical records.

A total of 379 participants developed ADHD, and 387 were identified as obese during the study period. The mean age of ADHD diagnosis was 10.4 years. To examine the association between ADHD and subsequent development of obesity, the investigators analyzed the data for participants with ADHD who were not obese at their time of diagnosis.

Girls with ADHD were significantly more likely than their controls to become obese by their mid-20s (hazard ratio 2.02; 95% CI 1.13-3.60; P=0.02). The association was not statistically significant for boys (HR 1.41; 95% CI 0.97-2.05; P=0.07).



Kumar and colleagues also looked for a link between the use of stimulant drugs used to treat ADHD in childhood and obesity in adulthood, but found no significant association (HR 0.85; 95% CI 0.52-1.39; P=0.52).

"The association between ADHD and obesity may reflect shared underlying abnormalities in the neural dopaminergic pathways that mediate not only impulse control and reward sensitivity but also appetite and satiety. In addition, poor executive functioning in individuals with ADHD may lead to less regular eating patterns, overeating, impulsivity, as well as decreased physical activity, thereby leading to excessive weight gain," Kumar and colleagues said. Sleep difficulties, which are often present in children with ADHD, could also lead to excess weight gain as a result of behavioral and hormonal factors, the investigators noted.

"Our finding of sex-specific differences in the association between ADHD and obesity may be partly related to unique differences in ADHD subtypes, such as the higher prevalence of the inattentive subtype of ADHD in females versus the hyperactive/impulsive subtype, which is more prevalent in males, as well as differences in associated comorbidities between male and female patients," Kumar and colleagues wrote.

Girls with ADHD tend to have lower self-efficacy and poorer coping strategies, as well as higher rates of depression, anxiety, and eating disorders, which may contribute to excess weight gain, the investigators said. In addition, the increased resting energy expenditure in boys with the hyperactive/impulsive type of ADHD might be protective against weight gain, they suggested.

"Parents and health care providers should be aware of this association and be proactive in taking measures to prevent obesity from developing," Kumar said in an interview with MedPage Today. "Healthy eating and an active lifestyle should be part of the routine care of children with ADHD even if they are not obese or overweight at the time."

As far as the lack of an association between stimulant treatment for ADHD in childhood and obesity in adulthood, "We can't say that these drugs are perfectly safe overall, but there appears to be no need to worry in terms of their impact on adult obesity," Kumar said.

In their analyses, the investigators adjusted for factors including birth weight and maternal age at birth, but limitations of the study include that they did not adjust for socioeconomic status or comorbidities such as anxiety, depression, and eating disorders that are common both to patients with ADHD and obesity, the researchers said.