ADHD Prevalence Rises, but Reasons Remain Unclear

Megan Brooks

September 04, 2018

The estimated number of diagnosed cases of attention-deficit/hyperactivity disorder (ADHD) increased significantly during the past 20 years, new research shows.

However, investigators note that the reasons behind the increase need to be better understood. Factors that may partly explain it include increased physician awareness of ADHD, changes in diagnostic criteria, and increased public awareness and better access to healthcare services, which could lead to a higher likelihood of ADHD diagnosis.

The study was published online August 31 in JAMA Network Open.

Major Jump

Wei Bao, MD, PhD, of the University of Iowa, Iowa City, and colleagues analyzed long-term trends in the prevalence of formally diagnosed ADHD cases among US children and adolescents during the past 2 decades.

They analyzed data on 186,457 youths aged 4 to 17 years who participated in the National Health Interview Survey (NHIS) from 1997 to 2016. The NHIS is a nationwide, population-based, cross-sectional survey conducted annually by the Centers for Disease Control and Prevention's National Center for Health Statistics.

The estimated prevalence of ADHD was 6.1% in 1997-1998 and jumped to 10.2% in 2015-2016, the authors report. Increasingly, more boys than girls were diagnosed with the disorder, as expected.

Table. Estimated Prevalence of Diagnosed Cases of ADHD in US Children

  1997-1998 2015-2016
Overall 6.1% 10.2%
Boys 9.0% 14.0%
Girls 3.1% 6.3%

 

The prevalence of diagnosed cases of ADHD in US children and adolescents was related to race/ethnicity, family income, and geographic region, although from 1997 to 2016, the prevalence increased with respect to all of these fctors.

In 2015-2016, with respect to differences by race/ethnicity, ADHD was diagnosed more among non-Hispanic white youths (12.0%) and non-Hispanic black youths (12.8%) than among Hispanic youths (6.1%).

With respect to family income, significantly more youths whose family income was less than the federal poverty level were diagnosed with ADHD (12.9%) than those at or above the federal poverty level (family income to poverty ratio of 1.0-1.9, 10.2%; family income to poverty ratio of 2.0-3.9, 10.0%; and family income to poverty ratio ≥4, 9.4%).

With respect to geographic region, the Western United States had the lowest rate of ADHD (7.0%), the Midwest had the highest (12.2%), and the Northeast (10.3%) and South (11.1%) were in the middle.

Pay Attention to ADHD

In an accompanying editorial, Daniel Dickstein, MD, of the Bradley Hospital PediMIND Program, Brown University, Providence, Rhode Island, notes that knowing the long-term trends in the prevalence of ADHD in the United States has important implications for healthcare and educational policy, funding, and research. In this context, this study "fills an important need."

Although this study indicates an increase in diagnosed cases of ADHD in the United States during the past 20 years, "we do not know whether this represents an actual increase in ADHD itself or changes in other factors affecting ADHD prevalence," Dickstein writes.

However, "taken as a whole, this study suggests we should keep paying attention to ADHD because many important unknowns remain," he says.

"These include ways to improve the effectiveness of how we diagnose and treat ADHD in the real world for all, not just those who can pay out of pocket, through policy and research geared at improving the quality of mental health care," he writes.

"We also need to understand why our medication and behavior treatments are quite effective in reducing ADHD target behaviors of impulsivity, inattention, and hyperactivity, yet data show that not all children have clear-cut improvements in academic achievement over the long haul," Dickstein says.

With this study showing that the prevalence of ADHD may be on the rise, "the answers to these questions are all the more important for the children and families of today and of tomorrow," he concludes.

The study had no funding. The authors and Dr Dickstein have disclsoed no relevant financial relationships.

JAMA Network Open. Published online August 31, 2018. Full text, Editorial

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