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Arnold School of Public Health


Robert McKeown publishes two studies that reveal new insights on ADHD prevalence and symptom trends

March 4, 2015 | Erin Bluvas, bluvase@sc.edu 

Robert McKeown, Distinguished Professor Emeritus in the Department of Epidemiology and Biostatistics, has had a productive retirement so far. In addition to various appointments and projects, he recently published two collaborative studies on the symptoms and trends of attention deficit/hyperactivity disorder (ADHD) based on his long-term research.

The first study, published in the Journal of Attention Disorders, followed a sample of children from elementary to high school through a 10-year South Carolina-based project funded by the Centers for Disease Control and Prevention (CDC) entitled Project to Learn about ADHD in Youth (SC PLAY). The researchers found that the persistence of ADHD symptoms over time varies depending on the category of the symptom. Inattentive symptoms tended to persist through adolescence while hyperactive/impulsive symptoms were more likely to diminish in number. Although boys were inclined to have a higher number of symptoms, the pattern of persisting or diminishing symptoms held true for both boys and girls. “These findings help clinicians, who are seeing increasing numbers of older adolescents and adults presenting with ADHD symptoms, understand how the presentation of ADHD may change over time in children of different ages and in adults,” says McKeown. The researchers’ conclusions also reveal how maturation and the adoption of coping skills may influence how individuals with ADHD may experience symptoms over time.

The second study, published in the Journal of the American Academy of Child & Adolescent Psychiatry, combined the data from the first study with data from a second funded site in Oklahoma (OK PLAY) to examine how ADHD prevalence estimates were impacted by changing the criteria or case definition. For this study, the researchers wanted to determine the variation in ADHD prevalence when limitations resulted in less rigorous case definitions as well as assess the impact of newly updated ADHD diagnostic criteria. The team’s findings suggest that one of the recent diagnostic criteria modifications, changing the minimum age for presentation of symptoms from seven to 12, resulted in a substantial increase in the prevalence of children and adolescents who met criteria. On the other hand, the new criterion requiring only five symptoms for those aged 17 and older instead of six resulted in a very small increase in the prevalence estimate.

Researchers collect information on ADHD using a variety of approaches, each with their own data limitations, and clinicians are especially limited by time and resource constraints. Scientists have long suspected that these methodological challenges impact the resulting estimates of ADHD prevalence and trends. These findings assist researchers by actually quantifying the effects of modifying the criteria and help differentiate trends in prevalence estimates that may be due to changes in diagnostic criteria or research limitations from trends that represent real changes in the prevalence of the disorder. For example, during this project a research group in India contacted McKeown to inquire about the importance of collecting certain information or whether this additional data collection could be omitted to save money. The findings from these projects help answer those questions.

Together, these two studies provide researchers and practitioners with information on longitudinal trends and statistical evidence for what happens when data samples are incomplete or diagnostic criteria are applied in different ways. Understanding the influence of using various data and criteria for determining prevalence and symptom trends can help clinicians make more informed diagnosis and treatment decisions.

For McKeown, the most important lesson—the one he comes back to with every project—is what a delight it is to work with these research teams. “I have been extraordinarily fortunate in the colleagues and students I have been privileged to lead,” says McKeown. “They are, without exception, dedicated, bright, creative, insightful, conscientious people who make my life immeasurably easier and our work so much more productive than it would be otherwise.”

Joseph Holbrook, lead author on the symptom persistence project, provides a perfect example. Holbrook was an Arnold School doctoral student under McKeown’s supervision when the project began, and he used the data for his dissertation. “I believe that the CDC recognized the quality of Joe’s work early on and came to rely on him often for analysis or information that they needed from the data,” says Mckeown. “As a result, as soon as he finished his degree, he was offered a position in the National Center on Birth Defects and Developmental Disabilities—the CDC unit that had funded the research.” McKeown was then fortunate to continue this work with Holbrook and other members of that team.

Additional co-authors on the studies include: Journal of Attention Disorders: Steven P. Cuffe (University of Florida College of Medicine-Jacksonville); Bo Cai (Arnold School of Public Health), Susanna N. Visser (Centers for Disease Control and Prevention), Melinda S. Forthofer (Arnold School of Public Health), Matteo Bottai (Karolinska Institute, Sweden), Andrew Ortaglia (Arnold School of Public Health); Journal of the American Academy of Child & Adolescent Psychiatry: Joseph R. Holbrook (Centers for Disease Control and Prevention), Melissa L. Danielson (Centers for Disease Control and Prevention), Steven P. Cuffe (University of Florida College of Medicine-Jacksonville), Mark L. Wolraich (University of Oklahoma), Susanna N. Visser (Centers for Disease Control and Prevention).