Paradoxically, investigators from the Johns Hopkins Bloomberg School of Public Health found that children treated with stimulants for ADHD initially experienced slower body mass index (BMI) growth than their undiagnosed or untreated peers. Then children with ADHD experience a rapid rebound of BMI that surpasses that of children with no history of ADHD or stimulant use and that could continue to obesity.
The study, thought to be the most comprehensive analysis of ADHD and stimulant use in children to date, found that the earlier the medication began, and the longer the medication was taken, the slower the BMI growth in earlier childhood, but the more rapid the BMI rebound in late adolescence — typically after discontinuation of medication.
Researchers concluded that stimulant use, and not a diagnosis of ADHD, was associated with higher BMI and obesity. The study is published in the peer-reviewed journal Pediatrics.
“Our findings should motivate greater attention to the possibility that longer-term stimulant use plays a role in the development of obesity in children,” said Brian S. Schwartz, M.D., M.S., lead author of the study.
“Given the dramatic rise in ADHD diagnosis and stimulant treatment for it in recent decades, this is an interesting avenue of research regarding the childhood obesity epidemic, because the rises in each of these roughly parallel one another.”
Previous research has found substantial evidence that stimulant use to treat ADHD is associated with growth deficits, and some evidence of growth delays.
However, the reported associations of ADHD with obesity in both childhood and adulthood was paradoxical and somewhat unexplained.
The results of this study suggest it is likely due to the strong influence that stimulants have on BMI growth, with delays in early childhood and a strong rebound in late adolescence.
Researchers also found evidence that unmedicated ADHD is associated with higher BMIs, but these effects were small.
ADHD is one of the most common pediatric disorders, with a nine percent prevalence among children in the U.S., and ADHD medication is the second most prescribed treatment among children.
Over the past 30 years, treatment for ADHD with stimulants has increased rapidly. From 2007 to 2010, 4.2. percent of children under age 18 had been prescribed stimulants in the past 30 days, more than five times the amount prescribed to the same-aged children between 1988 and 1984.
The study analyzed the electronic health records of 163,820 children, ages three to 18, in the Geisinger Health System, a Pennsylvania-based integrated health services organization. The research geographic area included 37 counties in central and northeastern Pennsylvania.
There were an equal number of boys and girls. Nearly seven percent — 11,080, or 6.8 percent — had an order for stimulants. (13,789, or 8.4 percent, received a diagnosis of ADHD. A total of 15,473 were prescribed stimulants, some for other reasons.)
There were 201,854 orders for the ADHD medications used in the analysis. The median age at first stimulant use was 8.5 years. Median use was 183 days, with 50 percent of children taking stimulants for less than six months and 50 percent of children for more than six months.
The researchers compared the BMI trajectories of those who had never had a diagnosis or prescription (the “controls”) with three groups: 1.) those with a diagnosis but no stimulant prescription; 2.) those with orders for stimulants without an ADHD diagnosis and 3.) those with both an ADHD diagnosis and stimulant orders.
Those in group three had slower rates of BMI growth in early childhood, with more rapid rates during adolescence that eventually exceeded those of the controls. Those with a diagnosis of ADHD but no stimulant orders had more rapid BMI growth after age 10 versus the controls, but the effects were small.
“Stimulant use was strongly implicated,” said Schwartz.
“The earlier stimulants were started and the longer they were used, the stronger was their influence on the degree of both the delayed BMI growth in early childhood and the rebound BMI growth in late adolescence. This is an important unintended consequence of stimulant use in childhood.”