A Nationwide Study of Attention‐Deficit/Hyperactivity Disorder Drug Use among Adults in I celand 2003–2012

In this study, we leveraged on complete nationwide prescription data for the total adult population in Iceland (N = 227,000) to examine how attention‐deficit/hyperactivity disorder ( ADHD ) drugs have been used over the past decade. In particular, we aimed to describe the prevalence, incidence and duration of use of stimulants and atomoxetine, among adults (≥19 years) in Iceland, with regard to sex, age, type of drug and specialty of the prescribing physician. Our results indicate that the 1‐year period prevalence of ADHD drug use rose, from 2.9 to 12.2 per 1000 adults between 2003 and 2012, with the most pronounced increases among young adults (19–24 years). The annual incidence increased 3 times, similarly among men and women. Extended‐release methylphenidate formulations were the most commonly used ADHD drugs. Specialists in psychiatry initiated treatment in 79% of new adult ADHD drug users. The proportion of users still receiving treatment after 1 year varied from 43.0% (19–24 years), 57.2% (25–49 years) to 47.5% (50+ years). After 3 years, the corresponding proportions still on treatment were 12.4%, 24.5% and 24.3%, and after 5 years 7.9%, 15.9% and 16.8%. These results of increasing ADHD drug use and short treatment durations call for further investigation of the quality of treatment regimens for adults with ADHD and better follow‐up of patients treated with ADHD drugs.