Attention Deficit Hyperactivity Disorder (ADHD) is a lifespan disorder associated with considerable economic cost. While the economic burden of ADHD has been widely estimated, there is considerable variation in reported costs between studies, which typically focus on health outcomes only, lack adequate control and fail to correct for the influence of genetic and shared environmental factors. The aim of this study is to overcome these limitations to reach a fuller understanding of the economic burden of ADHD.

Using the Danish National Registers 5269 adults with a diagnosis of ADHD in adulthood who had not received a diagnosis in childhood were identified. Excluding cases with missing data, comorbid diagnoses, and cases without a same sex sibling free of any diagnosed psychiatric diagnoses, a final cohort was formed consisting of 460 sibling dyads. Using a cross-sectional method focusing on the year 2010, cost differences between each adult with ADHD and their sibling were calculated from data retrieved from health, education, crime, employment and social care registers.

Adults with ADHD had considerably lower disposable income and paid less tax than their siblings. They also received more state benefits, had higher costs for health, social care, and crime than their siblings. The total average costs difference for the year 2010 was 20,134 euros more than their sibling for each adult with ADHD.

ADHD is associated with considerable costs which are borne by both the individual and the state and underlines the need to consider the wider economic impact of ADHD beyond income and healthcare utilisation costs.