précis

• The average rates of ADHD in children are 5–10%, but in some states fewer than 1% are in treatment.

• Other factors that indicate greater likelihood of treatment include living in an urban area, having a well-funded special needs program in the schools, and living in an area with higher poverty rates.

• Areas with more psychiatrists are more likely to have more children in treatment for ADHD.

• There is a great likelihood of significant undertreatment in some areas, the study shows.

The percentage of children treated with stimulant medication for attention-deficit hyperactivity disorder (ADHD) varies greatly among states, and more widely among counties, according to a new study estimating the prevalence of stimulant treatment among both adults and children at national, state, and county levels. The findings are published in the November issue of Psychiatric Services.

According to the study, “Geographic Variation and Disparity in Stimulant Treatment of Adults and Children in the United States in 2008,” ADHD is associated with heightened risks of poor academic and vocational achievement, delinquency, and other comorbidities. Because stimulant treatment is effective in moderating these risks, geographic differences in identifying and treating the disorder that do not result from differences in prevalence of ADHD or other conditions treatable with stimulants are reasons for concern, the study stated.

Although the study only makes available information about treatment prevalence, it is distinct from other studies that have examined this issue, said Douglas McDonald, Ph.D., principal associate at Abt Associates, a public policy consulting firm, and lead author.

“We sought not only to document the extent and range of variation in stimulant treatment among states but also among counties,” McDonald told CPU. “Because we had information about 24 million prescriptions, we could develop estimates at the county level, unlike other studies that used smaller samples.”

McDonald said that he and coauthor Sarah Kuck Jalbert also explored the reasons for this observed variation in treatment. “We examined rates of treatment and their association with a number of characteristics of county populations,” he said. Those characteristics included education levels, poverty rates, ethnicity, funding for special education, percentage of population living in urban areas, percentage uninsured, existence of a prescription monitoring program, and availability of prescribers. “The third distinctive factor was that we examined treatment rates not just of children but of children and adults,” he added.

Study details

The study stated that an estimated 4.5% of children and 1.2% of adults purchased at least one stimulant prescription during 2008, but only half of them (2.5% of children and 0.6% of adults) were classified according to the researchers’ measure as being in treatment. Researchers obtained records from IMS Health for 24.1 million prescriptions for methylphenidate (Ritalin), dexmethylphenidate (Focalin XR), dextroamphetamine (Dexedrine), combined dextroamphetamine and amphetamine, and lisdexamfetamine (dimesylate). These prescriptions were written by 300,795 prescribers to 6,031,622 unique patients that included commercially insured, Medicaid and cash purchases. Nonstimulants prescribed for ADHD, such as atomoxetine (Strattera), were not included.

Retail pharmacies dispensed 97% of all stimulants sold in the United States during 2008, according to the study. The sample included all stimulant prescriptions dispensed that year by approximately 37,000 retail pharmacies, about 76% of all pharmacies in the United States.

Results

The study found that wide variation in treatment prevalence existed among states, in both children and adults. For example, among children, rates ranged between 0.4% (Alaska) and 5.1% (Delaware). For adults, the difference ranged from 0.2% in Alaska to 1.2% in Delaware.

There were small differences in regional treatment rates — the rates among children were slightly higher in the South (2.4%) and were lowest in the Midwest (2.2%).

Regional rates for adults were highest in the South (0.5%) and were 0.4% elsewhere. Within regions, however, rates differed significantly. In Maryland, for example, 2.7% of children were estimated to have been in treatment compared with 5.1% in neighboring Delaware, 3.6% in West Virginia, and 4.4% in Kentucky. Child treatment prevalence of ADHD was higher in more urban counties and in counties with larger proportions of non-Hispanic white residents, less-educated populations, higher poverty rates, higher average expenditures for special education programs in schools and higher prevalence of adults in treatment.

The rates of children in treatment were positively correlated with the county supply of pediatricians and, to a lesser extent, of family medicine practitioners, according to the study. Only 34% of children in treatment obtained any of their prescriptions from a psychiatrist, and 4% obtained them from a neurologist. Nearly all others got them from primary care providers. “Our analysis found that the strongest determinant of the prescription rate per 1,000 county residents was the availability of prescribers in that county, especially for children — primary care doctors and pediatricians, but not psychiatrists,” said McDonald. “Among adults, the availability of psychiatrists and family medicine practitioners was strongly correlated with prescription rate.” It’s not surprising that in counties with more psychiatrists, the rate of adult treatment by stimulant medications is higher, added McDonald. “If you don’t have many psychiatrists in an area, you are less likely to be treated, and probably less likely to be diagnosed with ADHD or another condition where stimulant treatment can be useful.”

Implications

The estimated rates for children with ADHD range from 5% to 10%, said McDonald. The study found that in California the estimated rates of treatment prevalence were 1%, he said. “If that’s the case, [based on] the 1% in California, that suggests substantial undertreatment,” McDonald said. The national average indicates that 2.5% of all children in the United States are being treated for ADHD. Several states are way below 1%, including California, Colorado, and Hawaii.

“There’s a huge variation state to state and when you look at counties, even greater,” he said. “I think differences this large cannot be explained by the prevalence of ADHD,” he added. “This has to be about treatment.”

McDonald added, “If treatment differs so greatly, the conclusion has to be [about] gaps in established clinical practice guidelines and actual guidelines, especially in primary care practices.”

“We assume this is the case because it is highly unlikely that the prevalence of ADHD varies widely from one county to the next,” he said. “Because we observe very wide variation in treatment rates among counties, this must indicate that diagnostic and treatment practices of clinicians differ — probably from one clinician to the next.”

Researchers concluded that better education and training for physicians may improve identification and treatment of ADHD, thereby reducing disparities in care for ADHD and other disabling conditions.

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McDonald DC, Jalbert SK. Geographic variation and disparity in stimulant treatment of adults and children in the United States in 2008. Psychiatr Serv 2013, Aug 2. Epub ahead of print. E-mail: doug_mcdonald@abtassoc.com.