Changes Seen in Patterns, Rates of Some Childhood Disabilities

The prevalence of childhood disability rose from 2001 to 2011, continuing a long-term trend, but there were some surprising details within that bigger picture.

Overall, the rate of disability for children from birth to age 17 rose from 6.87 percent to 7.94 percent, an increase of 15.6 percent. That represented an absolute rise from an estimated 4.9 million to 5.9 million children, based on parent-reported data covering about 199,000 children from the National Health Information Survey (NHIS), said Amy Houtrow, M.D., Ph.D., M.P.H., an associate professor of physical medicine and pediatrics at the University of Pittsburgh, and colleagues, online August 18 in the journal Pediatrics.

The rise was not due to physical health conditions, however. Their overall prevalence actually declined by 11.8 percent over the decade, led by a 24 percent drop in asthma or breathing problems and offset somewhat by nonsignificant rises in hearing, vision, and musculoskeletal problems.

However, disabilities attributable to neurodevelopmental or mental health conditions increased by 20.9 percent.

Under that general heading, though, there were notable categorical shifts. “Learning disabilities” declined by 13 percent but “speech problems” (up 63 percent), “mental retardation” (up 63 percent), and “other” mental, emotional, or behavioral problems (up 65 percent) rose sharply.

“Using a large, representative sample like the NHIS, an inclusive definition of disability, and a longitudinal approach gives us confidence in their data,” said psychiatric epidemiologist Linda Cottler, Ph.D., M.P.H., a professor and chair of the Department of Epidemiology in the College of Medicine and College of Public Health and Health Professions and a professor in the Department of Psychiatry at the University of Florida.

However, changes in diagnostic definitions and even the wording of questions represent limitations, as the authors acknowledge. For instance, the term “intellectual disability” was added to the question on “mental retardation” in 2011.

The root of the changes in disability rates may lie in a broad range of factors, including biological, social, or cultural ones.

“The whole field now is trying to assess change over time—when it’s real and when it’s not,” Cottler told Psychiatric News. “Epidemiological science offers us different ways we can look at causation. Is the phenomenon biologically plausible or is there some spurious association? Is there a confounder? The best way to confirm such findings is by replication, so other studies must now focus on the replicability of these findings.”

Diagnostic shifts may partly account for the decrease in learning disabilities and the increase in other neurodevelopmental or mental health problems, said Houtrow and colleagues. Other factors at work may include increased awareness of mental health problems or the need for a diagnosis in order to receive therapeutic services or accommodation at school.

Another notable—and unexpected—outcome of the study was the split between high-income and low-income families.

As expected, children at the lower end of the income scale (below 100 percent of the federal poverty level [FPL]) had a higher prevalence of disability. But those at the highest end (at least 400 percent of the FPL) showed the greatest increase over the decade (38 percent), a finding that surprised the researchers.

Better access to care or greater willingness to seek services among higher-income families, among other possibilities, may account for the differences. Such differences raise important points for future research and the ability to compare findings across time and across studies. Stability in the diagnostic criteria and the definition of disability are needed to derive meaningful comparisons.

“Additional research is necessary to assess the impacts of changing diagnostic labels and thresholds, evolving cultural views of health and disability, variable access to health services, the contribution of provider biases, and the incentive for a diagnosis to receive services,” said Houtrow.

“Further research is needed to more fully understand the implications of the current findings on the development of programs and services designed to best meet the needs of children,” commented child psychiatrist David Fassler, M.D., a clinical professor of psychiatry at the University of Vermont College of Medicine in Burlington.

A chart on the rates of neurodevelopmental and mental health conditions rising in youth can be accessed here. ■