Research

Overview

Attention-Deficit/Hyperactivity Disorder (ADHD) is a serious public health problem because of the large estimated prevalence¹ of the disorder, significant impairment in the areas of school performance and socialization, the chronic nature of the disorder, the limited effectiveness of current interventions to attend to all the impairments associated with ADHD, and the inability to demonstrate that intervention provides substantial benefits for long-term outcomes.

However, because of the evolution of the case definition and differences in how the case definition is operationalized, there is disagreement as to prevalence and precise characteristics of children with the disorder.

Due to the lack of a single, consistent, and standard research protocol for case identification, variable and disparate findings have been noted in the literature. Consequently, relatively little is known about the etiology of ADHD, although genetic factors are believed to be important contributors.

 

Current Research

Project to Learn About ADHD in Youth (PLAY)

Because of increasing concern and awareness among health professionals and the public alike, CDC’s National Center on Birth Defects and Developmental Disabilities (NCBDDD) is funding a joint collaboration research project with the University of South Carolina and the University of Oklahoma Health Sciences Center to conduct population-based research on ADHD among school-aged children.

Recognizing that many uncertainties remain concerning prevalence, etiology and treatment patterns of ADHD, this research will shed light on:

• Short and long-term outcomes of children with ADHD
• The prevalence and treated prevalence of ADHD in children
• The existence of comorbid and secondary conditions in children with ADHD
• The types and rates of health risk behaviors in children with ADHD
• Current and previous treatment patterns of children with ADHD

The result of this collaboration will be one of the largest community-based, epidemiologic studies of ADHD in the United States.

This data will also provide information critical to understanding the magnitude of the disorder, the expression of ADHD in diverse population groups, the receipt and quality of community care, and factors associated with differential outcomes in children with the disorder.

Study findings will not only enhance our understanding of ADHD in children, but will also increase our ability to make the most informed decisions and recommendations concerning potential public health prevention and intervention strategies. 

 

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Research Agenda

Public health issues in ADHD can be divided into three areas: the burden of ADHD in the population, epidemiologic research issues in ADHD, and concerns related to interventions for ADHD. These three topical areas were identified by CDC as crucial for examining ADHD, and necessary to address public health concerns and opportunities for action. Following are the key issues for each topic as well as the necessary actions to address these public health needs.

• Social and Economic Burden of ADHD through the Lifespan
• Epidemiologic Issues in ADHD
• Interventions for ADHD

 

Social and Economic Burden of ADHD through the Lifespan

Issues
Given the nature of the disorder, ADHD is believed to have a noticeable impact on social, economic, educational, and health care delivery systems. Additionally, it is reasonable to assume the condition affects those socially associated with an ADHD individual, including his/her family members, peers, and co-workers. However, the magnitude of the social and economic burden in these areas has not been systematically documented.

In general, small, clinic-based studies have shown that adults with ADHD consistently exhibit problems with interpersonal relationships, often have difficulty with employment, and frequently have comorbid or secondary conditions that further debilitate. Perhaps many of the disabilities and poorer outcomes associated with ADHD actually are more strongly associated with conditions that are highly comorbid with ADHD (such as Conduct Disorder) and result in significantly higher economic consequences to society. However, this hypothesis has not been tested.

In understanding the full nature of the disorder, it is imperative to understand the effect it has on the families of children with ADHD. These families may be more prone to conflict and increased levels of familial stress. The child with ADHD may also reduce the parents' productive participation in activities outside the family (work and community life). Many parents of children with ADHD themselves have the disorder or considerable levels of the symptomatology. However, the impact this disorder has on the family unit and in adult life needs considerable research effort to clarify what aspects of family it impacts and in what ways.

In addition, there is little concrete knowledge of the degree to which interventions can or do improve the outcome of children with ADHD. Developing ways to improve outcomes must begin with consistent and standardized measures of the impact of the disorder. Such methodical surveying has not occurred. Development of standardized burden measures is critical to beginning this process.

Action to Address Public Health Needs

• Conduct analyses of ADHD public health burden in a way that estimates a broad array of costs outside of those exclusively associated with medical treatment. The burden should be studied from a broad perspective to include estimations of cost to society in a monetary sense as well as to individual-level indicators of well-being such as family functioning and social relationships.
• Develop a standardized way to measure burden associated with ADHD and promote its use across studies. This would enable cross-study comparisons such as meta-analysis to be undertaken. This standardized measure should account for medical/treatment costs, educational costs, family costs, and adult functioning variables.
• Incorporate information on ADHD in efforts to study and prevent unintentional injuries, alcohol and drug abuse, sexual risk-taking, disability, and other health risk behaviors in which ADHD may play an important role.
• Include standardized measurements of burden in all public health research of ADHD. Future efforts to measure the impact of ADHD across a cohort should be a priority. Understanding if current interventions or future prevention strategies result in burden reduction will depend largely on consistent and accurate estimation of these burdens.
• Efforts must be made to estimate the prevalence and cost of this disorder in adult populations to understand the strict monetary costs as well as to better understand the areas of impairment for adults with ADHD.
• Conduct population-based ADHD research that includes information on comorbid conditions and the burden with which they are associated. Much of our current evidence regarding comorbid conditions comes from clinical studies rather than population-based studies.
• Explore mechanisms to append economic and social burden studies on other ongoing or completed studies in order to quantify the burden of ADHD.
• Foster collaborations across Federal agencies in order to include information on ADHD in data collection efforts.
• Establish a resource for both professionals and the public regarding what is known about the impact of ADHD.

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Epidemiologic Issues in ADHD

Issues
Although investigation of ADHD has been quite extensive over the past 30 years, the scientific process has been significantly slowed by the lack of a single, consistent, and standard research protocol for case identification. Variable and disparate findings have been noted throughout the literature even on basic issues such as prevalence. As a consequence, speculation regarding possible increases in ADHD prevalence cannot currently be evaluated.

Additionally, we do not have demographic and descriptive statistics for children and adults with the disorder; therefore, there are disparities in identification, access to treatment, and reports of the manifestation of ADHD and its comorbidities. Risk factors for ADHD have not been thoroughly investigated although some clinical samples have identified possible factors that may contribute to ADHD. Some of these related factors are prenatal alcohol use, prenatal smoking, and low birth weight. Genetic predisposition or family history of ADHD has been noted consistently among clinical samples as a risk factor for the development of ADHD.

Unfortunately, many fundamental etiologic questions remain for ADHD. Identifying and understanding etiologic factors will enhance prevention efforts and treatment for both children and adults with ADHD.

Action to Address Public Health Needs

• Develop standard case identification protocols for use in research projects.
• Conduct etiologic studies of ADHD using population-based approaches to identify important risk factors and opportunities for prevention activities and research.
• Use observational epidemiologic methods to describe the impact of ADHD, its impact, and its intervention patterns at the population level.
• Utilize scientific findings to develop, design, and implement ADHD prevention efforts where possible.
• Identify current national or regional surveys where adding ADHD questions would provide particularly useful information regarding the magnitude of the disorder, the nature of common comorbidity and/or secondary conditions, as well as data on health risk behaviors and long-term outcomes for those with ADHD.
• Establish a Federal interagency workgroup to pool research expertise and resources in order to launch epidemiologic research efforts that address the public health research needs in ADHD. Such collaborations should be multi-disciplinary and include professionals in epidemiology, mental/physical health, risk behavior prevention, and health communication for example.
• Establish a resource for both professionals and the public regarding what is known about the epidemiology of ADHD.

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Interventions for ADHD

Issues
ADHD is a chronic condition of high prevalence that requires long-term intervention. Because ADHD is an impairing condition and can have lifelong consequences, interventions designed to reduce negative outcomes and increase capacities should be carefully considered at the national level. One key public health concern is the safety of pharmacological interventions. A second key concern is the effectiveness of current interventions to reduce the impairment associated with ADHD thereby improving health and functioning for ADHD individuals over time. A third public health concern is access to appropriate interventions for individuals and families affected by the disorder.

There are several public health concerns relative to pharmacotherapy. Pharmacologic treatment is extremely prevalent. Assessing the health risks and benefits to young children, particularly preschoolers, is a high priority. Children who begin medication therapies very early and receive treatment on a long-term basis may have unknown risks associated with current treatments. Additionally, pharmacologic interventions often do not normalize behavior. Research, albeit limited, suggests that even with long-term treatment, children and adults with ADHD experience substantial problems in the school, home, workplace, and community settings. This raises questions about the effectiveness of pharmacologic interventions as a long-term approach.

Another intervention option to treat ADHD is behavior modification. It is clear that behavior modification therapies, for youth in particular, have been tested and shown beneficial for the treatment of behavioral disorders including ADHD. However, the majority of youth receiving psychological interventions for ADHD are probably receiving treatments that have not been shown to be effective, such as individual therapy and/or play therapy. The effectiveness of behavioral interventions must be further studied in the treatment of ADHD, to better understand their potential to normalize the behavior and functioning of those with the disorder, especially when combined with pharmacotherapy.

Access to interventions is a critical public health concern. ADHD affects a person's ability to learn and be socialized to his/her potential; therefore access to diagnosis and intervention is a necessity. Common barriers to services include lack of insurance coverage for mental health problems, exclusion of behavior disorders, including ADHD, from mental health coverage, and under-identification or mis-identification. Community practice with respect to the diagnosis of ADHD fails to uniformly employ accepted methods for establishing cross-situational symptomatology, measurement of functional impairment, and diagnosis of comorbid conditions. Nationally, we must begin to look at a wide variety of intervention issues surrounding ADHD, including how current interventions impact individuals and systems over time, as well as problems with access to appropriate services.

Action to Address Public Health Needs

• Disseminate educational materials relating to the diagnosis of and intervention opportunities for ADHD. Recipients should include but would not be limited to primary care physicians, physician extenders (NP's and PA's), mental health professionals, and educators.
• Promote the necessity of careful case identification using standardized instruments and the employment of the most effective interventions in common practice by disseminating useful information to professionals and the public related evidence-based interventions for ADHD.
• Conduct population-based studies of ADHD intervention practices to examine such variables as age of initiation of treatment, type(s) of treatment, duration of treatment, and barriers to receipt of services.
• Establish a mechanism (possibly a registry) of treated individuals to monitor the health effects and potential benefits of long-term treatment for ADHD, particularly among pre-school age children. Additionally collect other related outcomes such as school attainment, interface with judicial system, work performance, and other pertinent variables.
• Collaborate with other organizations to educate and promote what is known about ADHD interventions, appropriate standards of practice, their effectiveness, and their safety.
• Establish a resource to the public for accurate and valid information about ADHD and evidence-based interventions.

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Public Health Perspective

CDC acknowledges the need for further research in ADHD.  Specifically, key public health questions yet to be answered include:

• What are the causes and risk factors of ADHD? What is the prevalence of ADHD? Is the prevalence increasing?
• What social and economic impacts does ADHD have on families; schools; the workforce; and judicial and health systems?
• Are ADHD and its comorbidities being appropriately diagnosed and treated? Are people with ADHD able to access appropriate and timely treatment?
• How effective are current interventions? What are the long-term effects of drug treatments?

 

Footnote

1 Although the DSM-IV (1994) cites a prevalence rate of 3-5% of school age children, methodological issues in epidemiological research and the evolving dynamics of the disorder have led to wide variations of reported prevalence estimates that range from approximately one percent to nearly 20 percent of school age children.