Researchers who followed more than 15,000 young Americans from adolescence into adulthood found that the symptoms of
attention-deficit/hyperactivity disorder (ADHD) in childhood are linked to an increased risk of obesity in adulthood, and that the
greater the symptoms, the higher the risk.
The study was the work of researchers from Duke University Medical Center in Durham, North Carolina, and was published in the advanced online issue of the International Journal of Obesity in late October.
Co-author Dr Scott Kollins, who is director of the Duke ADHD Program, told the press that this was the first study to show that it's not just the diagnosis of ADHD that matters, but the symptoms, that is the amount of hyperactivity, inattention and impulsivity of the behaviors associated with ADHD.
Lead author Dr Bernard Fuemmeler, who is director of the Pediatric Psychology & Family Health Promotion Lab in the Department of Community and Family Medicine at Duke said "it's a dose effect":
"We showed that as the number of symptoms increase, the prevalence of obesity also increases," he added.
The researchers found that having three or more of any of the symptoms of ADHD significantly increased the odds of being obese.
For the study, they examined data on 15,197 adolescents taking part in the National Longitudinal Study of Adolescent Health (Add Health), a nationally representative sample (including Hawaii and Alaska) of American adolescents followed from 1995 when they were in high school (in grades 7 to 12) to 2009, when they were in their mid-20s to early 30s.
Add Health has an enormous set of data, gathered in four "waves" that included comprehensive in-home interviews, physical measurements, and biological specimen collection.
During wave III, which took place in 2001-2002, when the participants on average were in their early 20s, they were also asked questions on "Retrospective ADHD", which essentially asked them about any ADHD symptoms, such as inattention, hyperactivity and impulsivity, in their childhood when they were aged between 5 and 12.
Fuemmeler and colleagues looked for any links between these retrospective ADHD symptoms of childhood and physical measurements in adulthood, which were taken in wave IV of Add Health, conducted in 2007 and 2008, when the participants were aged beween 24 and 32.
They found that:
- The number of inattentive and hyperactive/impulsive symptoms in childhood went up in line with increasing waist size, BMI, and blood pressure (diastolic and systolic) in adulthood, such that more symptoms were linked with higher waist size, BMI and blood pressure.
- After taking into account demographics, exercise, use of alcohol and tobacco, and depressive symptoms, participants who had three or more inattentive and hyperactive/impulsive symptoms in childhood had the highest odds of being obese in adulthood.
- Among participants with only hyperactive or impulsive symptoms in childhood, the odds of being obese in adulthood was 63 per cent.
- Hyperactive or impulsive symptoms were also tied to greater weight gain in the transition from adolescence to adulthood.
Fuemmeler said that research like this may give us some ideas about what's driving the obesity epidemic.
"The findings support the idea that certain self-regulation capacities, like the ability to regulate one's impulses, could be a relevant trait to understanding why some people may be more vulnerable to obesity," he said.
The researchers concluded that while there appeared to be a link between ADHD symptoms and high blood pressure, it was more likely to be related to weight rather than ADHD symptoms.
"The most exciting thing about this research is it gives us a thread to follow in determining why kids with ADHD symptoms might be at risk for developing obesity."
"It establishes the path for identifying these kids earlier and focusing on intervention methods," he added.
"Association between attention-deficit/hyperactivity disorder symptoms and obesity and hypertension in early adulthood: a population-based study."
B F Fuemmeler, T Østbye, C Yang, F J McClernon, S H Kollins.
International Journal of Obesity Advanced online publication 26 October 2010.
Additional sources: Add Health (UNC), Duke Medicine News and Communications.
Written by: Catharine Paddock, PhD