The Changing Epidemiology of ADHD

An Expert Interview With Susanna Visser, MS

Laurie Scudder, DNP, NP


January 13, 2011

Data From the National Survey of Children's Health 2007

Editor's Note:

The results of the second administration of the 2007 National Survey of Children's Health (NSCH) have been reported in the Morbidity and Mortality Weekly Report.[1] The report documented an almost 22% increase in the percentage of children 4-17 years of age with a parent-reported diagnosis of attention-deficit/hyperactivity disorder (ADHD). These findings illustrate the substantial impact of ADHD on both families and pediatric providers. Laurie Scudder, DNP, NP, of Medscape sat down with Susanna Visser, MS, Lead Epidemiologist, National Center on Birth Defects and Developmental Disabilities, US Centers for Disease Control and Prevention, Atlanta, Georgia, to discuss the report.

Medscape: Ms. Visser, can you begin by summarizing the main findings of the 2007 NSCH study?

Ms. Visser: The primary goal of this particular report was to compare the most recent parent-reported survey results from a national survey conducted by the US Centers for Disease Control and Prevention (CDC) sponsored by the Maternal and Child Health Bureau at the Health Resources and Services Administration (HRSA) with an earlier survey. The first survey was conducted in 2003-2004 and had 102,000 respondents. It was repeated in 2007-2008 with approximately 92,000 respondents. This large sample size allowed us to drill down into issues of child health in a way that we cannot in other surveys or through other mechanisms.

The specific question presented to parents was: "Has a doctor or health professional ever told you that your child has ADD [attention-deficit disorder] or ADHD?" Extrapolating from the survey responses to the total US population, it was determined that 4.4 million children in the United States between the ages of 4 and 17 years had received a diagnosis of ADHD as reported by their parents in 2003. By 2007, that estimate had risen to 5.4 million children. That represents an increase of 1 million children with a parent-reported diagnosis of ADHD in approximately 4 years. That is a 22% increase over that time period and, obviously, was a number that was large and surprising. We knew that the rates were probably increasing because of our previous work, but this was a jump that really caught our attention.

Medscape: Can you describe the various stakeholders in this study and the reaction of these different groups?

Ms. Visser: At the CDC, our main goal through the use of these surveys is to keep a pulse on the health of the nation, and so what we have found here suggests that there is a growing need among American families as a result of this increase in children with ADHD. A child with ADHD may have symptoms of inattention and hyperactivity or impulsivity, or both. Regardless of the symptoms, ADHD can cause significant functional impairment problems at home, at school, or with friends. From a public health perspective, there are implications resulting from 5.4 million American children with ADHD. As most parents can appreciate, if you have a child with a behavioral disorder, it affects everything about that family's life, from the expectations of what a typical day is going to be like, through the expectations for school achievement, to relationships with family and friends. It can pose a number of very difficult challenges for those families. Healthcare providers are going to need to help the large number of families address the concerns that are brought into the clinical setting.

Medscape: What was the reaction of the healthcare community to this finding?

Ms. Visser: I think that clinicians -- psychologists and healthcare providers who are diagnosing, treating, and managing children with ADHD -- believed that, although this is a very large number, it was consistent with their clinical experience. Although it is surprising to think that nearly 1 in 10 children have had a diagnosis of ADHD, it is consistent with the clinical experience. They are managing a lot of children with ADHD, with 2.7 million children taking medication in 2007.

Children typically don't just come in for a diagnosis. They are starting down a treatment and management path that we hope will include a behavioral component in addition to medical management, but we are unable to determine that from these data.

To answer your question, I think that healthcare providers believed that this was clinically consistent with what they have been seeing, and that the number, although quite large, does represent the burden of ADHD that they are seeing relative to other conditions in their practices.

Medscape: You also found some very interesting subgroup findings in different demographic groups. Could you share those findings with us?

Ms. Visser: These data confirmed previous population-based studies that revealed a 2:1 or even a 3:1 ratio of boys to girls in terms of diagnostic prevalence. That consistency really gives us a validity check. In this survey, we noted a 2.3:1 ratio of boys to girls for ever having been diagnosed with ADHD on the basis of parent report; that increases slightly to 2.6:1 for a current ADHD diagnosis. That has been very consistent in the literature and suggests that these data have some face validity. We also noted that the rates of ADHD increased with age, and that makes sense because parents were asked whether they had ever been told that their children had ADHD. Thus, those percentages should trend upward with age, and that was consistent.

We saw some interesting subgroup findings that were unique. The first was with respect to age. When we looked over time, although there were significant increases in ADHD prevalence in all of the 3 age groups that we looked at (4-10, 11-14, and 15-17 years), we saw that the 15- to 17-year-olds had a disproportionately greater increase when compared with younger children. This suggests that clinicians are probably seeing more older teens for diagnosis, treatment, and management of ADHD than in the past, and we do not have a clear understanding of why.

It may be that there is a decrease in stigma around ADHD, a greater acceptance of available treatment protocols, or increasing demands on students with greater expectations to go on to college. Children who were able to adapt to the difficulties presented by their ADHD symptoms at younger ages may have a more difficult time adapting at older ages, and the availability of more flexible treatment options may increase the likelihood that these children seek diagnosis and treatment. I think that that could be behind it. However, we do not know, and we are definitely looking to the clinical community to help elucidate that finding.

We also saw some interesting patterns across ethnic groups. Historically, in the United States, rates of ADHD have been lower in Latinos compared with non-Latino groups. Although these data confirmed that lower rate, we did see a large increase, about 53%, from 2003 to 2007 among Latinos. I think that is an important finding and suggests that the cultural differences in ADHD diagnosis or treatment may be lessening. That is an important finding to keep in mind.

Medscape: The other group who experienced a significant increase were children who were reported by parents to be multiracial.

Ms. Visser: That is correct. This is a finding that we have seen over time, and I am not sure what is behind this. There is limited literature about risk factors for ADHD and behavioral disorders in multiracial children. It is likely that the rates represent the coalescing of various social and economic risk factors within these families. However, it is not clear what is driving the findings among multiracial children.

Medscape: What about regional variance? I noted that the rate of parent-reported ADHD in North Carolina was 15.6% in this survey; however, in California it was only 6.2% -- which is obviously a dramatic difference.

Ms. Visser: That is correct. We saw a good bit of geographic variation in the rates of ADHD. Although there was a significant increase over time in the Northeast, Midwest, and South, there was not a comparable increase in the West. The regional differences were apparent at the state level, as you noted. We found that the state with the largest prevalence of parent-reported ADHD was North Carolina at 15.6%, representing nearly a 63% increase in ADHD prevalence from 2003 to 2007.

We found 3 other states with rates above 14%: Alabama at 14.3%; Louisiana at 14.2%; and Delaware at 14.1%. We are very interested in these states. We want to understand what is driving the rates up in specific states and reasons for the large variance across states. Some of our western states are quite low. In California, as you mentioned, only 6.2% of children are reported to have an ADHD diagnosis. It is important to us in terms of epidemiology to understand what is predicting both higher and lower rates of diagnosis within particular states.

We know that some of that can be accounted for by demographic factors. Risk for ADHD increases as income decreases -- a situation typically associated with lesser-resourced educational services, fewer support structures available to parents, and then more behavioral problems coupled with insufficient availability of appropriate resources and services. There are issues of access to care and limited resources to support a family in a way that will optimize the child's behavior. Those all coalesce together and relate to the environmental contributors to childhood ADHD.

Additionally, there is a genetic component to ADHD. In any population there will be a core group of children genetically predisposed to ADHD regardless of environmental factors.

It is important to understand that differences in state policies, practices, and things not related to the specific environmental and demographic factors within the state predict the diagnostic rate of ADHD, too.

We have been working with several states to try to understand the reasons for the state-level variation. We suspect that there may be very aggressive quality improvement practices and protocols in place in certain states with higher prevalence rates. When you screen more children for behavioral or developmental problems, you will find more symptoms. That greater rate of symptom identification will likely translate into greater rates of diagnosis. A state that has a higher rate is not necessarily in trouble. It may be that they are doing a fantastic job of assessing and screening the behavioral needs of their children, and that will translate to a higher rate of behavioral diagnoses. States that find themselves at the top of this list should not necessarily be concerned. It does underscore the importance of unpacking these findings to identify what is really driving these factors over time.


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