Liam Davenport

June 01, 2015

GLASGOW, Scotland — Adults with ADHD have lower incomes and higher education costs, and they place a greater burden on the state than their unaffected siblings, results of a UK/Danish study reveal.

Controlling for comorbid diagnoses and demographic characteristics, David Daley, PhD, professor of psychological intervention and behavior change at the University of Nottingham, and colleagues found that ADHD by itself costs society more than €13,500 ($14,731) per person per year.

The results, which were presented here at the 5th World Congress on Attention Deficit Hyperactivity Disorder (ADHD), suggest that the economic impact of ADHD should be taken into account when considering the affordability of early identification and treatment.

Pure Sample

Discussing the study along with coauthor Anne Mette-Lange, a clinical psychologist at Aarhus University, in Denmark, Dr Daley told Medscape Medical News that "nearly all" of the previous studies that have explored the costs associated with ADHD have been confounded in "multiple ways."

They are "either confounded by sample, because they rely on insurance databases and their biases, or confounded because they talk about the costs of ADHD without controlling for comorbidity," he said, adding: "As most clinicians know, it's actually quite rare to get a pure ADHD patient."

To estimate the costs uniquely associated with ADHD, the researchers examined data from the Central Person Register in Denmark, which contains information on approximately 5 million Danish adults.

The investigators initially identified 5331 individuals who had been diagnosed with ADHD in adulthood. They then removed from consideration all individuals who had comorbid disorders and matched them with a sibling without any psychiatric disorders. This yielded 365 pairs who had grown up in the same social environment with the same biological parents.

The team then conducted a 1-year snapshot health economic analysis using data for 2010, because that is the most recent year for which all the relevant databases in Denmark have been updated.

"Most of the literature in the past has been focused on health utilization, because it's been based on insurance databases, and they only have healthcare utilization outcomes," Dr Daley explained. "Here, we're able to look at both inpatient and outpatient and medication costs, but also to look at income, tax, crime, driving, and a whole range of outcomes that are not normally included in a lot of the healthcare economic outcomes."

Combining public and private costs, the researchers found that the cost difference to society of individuals with ADHD compared with their unaffected siblings who served as control participants was €13,608 ($14,844) per individual per year.

High Rates of Comorbidity

Dr Daley said that they did not want to extrapolate the costs further, explaining: "We've tried to get away from the sensational billion dollar headlines by multiplying by the prevalence rate, because I think that's somehow misleading. We'd like to focus this on the individual."

He suggested that for individuals who have ADHD and comorbid disorders, the cost to society would be even greater.

"If you have what would be quite a typical clinical presentation in adulthood of two or three different comorbid disorders...with ADHD and conduct disorder and maybe depression and anxiety, then those costs would clearly be greater."

"Whether the costs are arithmetic or geometric, it's difficult to say, but we certainly know that when we look at the demographic features of our ADHD sample...the average number of comorbid disorders was 4.3," Dr Daley added.

"That's quite high, because we're talking here about a group of adults who, although they had ADHD in childhood, they weren't diagnosed, and there is compelling research evidence to show that undiagnosed disorders early in childhood lead to the development of greater psychiatric problems later on."

Regardless, Dr Daley believes that the findings in individuals with ADHD alone make a "compelling" health economic argument for greater investment in education.

"A lot of the costs fall to the state, and they fall to the state in terms of what we would call economic productivity," he said.

"ADHD individuals are not in employment as often, they have a much lower disposable income, so they are not spending, they receive a much greater amount of tax credits, and they pay a lot less tax compared to their same-sex siblings," he added.

"The difference is actually quite remarkable when you think the only difference between these two groups of individuals is ADHD."

Clever Approach

Desiree Silva, MD, MPH, from the University of Western Australia, in Perth, who led the guided poster tour, underlined the importance of the findings.

Dr Desiree Silva

"Most of the time when we look at costs, all they do is they take a small sample and they just generalize it," she told Medscape Medical News.

She explained that comparing ADHD patients with their siblings, and thus removing family costs, "is a really clever way of looking at, because you get a much more accurate sum of what's actually the true cost burden."

She also believes that the methodology could be used in other studies ― for example, to examine the costs of ADHD in childhood.

In conclusion, Dr Silva agreed with the research team that the findings reinforce the need for early investment in ADHD identification and treatment. She said: "If you can improve their self- esteem and improve their education, which a lot of them struggle with, you are going to get a much better outcome the other end, because they'll be in employment, for a start."

The study was funded by the Rochwool Foundation. The authors and Dr Silva report no relevant financial relationships.

5th World Congress on Attention Deficit Hyperactivity Disorder (ADHD). Abstract P-14-009. Presented May 29, 2015.

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