As ADHD medication use has surged in Sweden over the past decades, evidence is needed on whether the benefit of the medication remains consistent. A new study from Karolinska Institutet, published in JAMA Psychiatry, shows that while ADHD medication still helps reduce the risk of self-harm, unintentional injuries, traffic accidents, and criminal behavior, its protective effects have diminished over time as ADHD medication use has broadened to a wider group of patients.
ADHD affects around 5% of children and 2.5% of adults worldwide and is linked to a range of adverse outcomes, including injuries, criminal behavior, and premature death. In recent years, the number of people diagnosed with ADHD and prescribed ADHD medication have increased dramatically. In Sweden alone, ADHD medication use increased nearly fivefold from 2006 to 2020, making the prescribing prevalence among the highest in the world. These significant shifts raise a critical question: does the growing and more diverse group of individuals receiving ADHD medication today, on average, benefit as much as those treated a decade ago?
Changes in medication effects over time
To answer this question, an international team led by researchers from Karolinska Institutet conducted a register-based study of more than 247,000 individuals in Sweden who used ADHD medication between 2006 and 2020. To assess the associations between ADHD medication and serious outcomes - self-harm, unintentional injuries, traffic accidents and crime - the researchers used a self-controlled case series design. In this approach, the risk of experiencing serious outcomes is compared within the same individual during periods when they were taking ADHD medication versus when they were not. Importantly, the researchers also compared these risks across three time periods: 2006-2010, 2011-2015, and 2016-2020 - a time during which ADHD medication use in Sweden increased from 0.6% to 2.8% of the population.
"We found that medication use was consistently linked to lower risks of self-harm, unintentional injuries, traffic crashes and crime throughout the 15-year follow-up period," says the study's first author Lin Li , postdoctoral researcher at the Department of Medical Epidemiology and Biostatistics , Karolinska Institutet. "However, the strength of these protective effects declined over time, coinciding with a sharp rise in prescription rates in the society."
Shifts in ADHD patient population
As awareness of ADHD has grown and the diagnostic criteria have broadened, the population receiving treatment has shifted. The researchers suggest that the diminishing effects of ADHD medication over time may reflect changes in who is being treated. Notably, the increase in prescribing has been particularly pronounced among adults and females. These shifts may in part explain why the average benefits of ADHD medication have declined over time.
"This does not mean the medications are no longer effective," says Dr. Zheng Chang , senior researcher at the Department of Medical Epidemiology and Biostatistics and the last author of the study, "But it does suggest that as the patient population has changed from 10 or 20 years ago, so we need to review the clinical guidelines and understand individual-level treatment effects to better inform clinical decision-making."
The study was done in close collaboration with Professor David Coghill from the Departments of Pediatrics and Psychiatry at the University of Melbourne and the Murdoch Children's Research Institute, Melbourne, Australia, and with Professor Henrik Larsson from the School of Medical Sciences, Örebro University.
Publication
Increased Prescribing of Attention-Deficit/Hyperactivity Disorder Medication and Real-World Outcomes Over Time. Lin Li, David Coghill, Arvid Sjölander, Honghui Yao, Le Zhang, Ralf Kuja-Halkola, Isabell Brikell, Paul Lichtenstein, Brian M. D'Onofrio, Henrik Larsson, Zheng Chang. JAMA Psychiatry. Published online June 25, 2025. doi:10.1001/jamapsychiatry.2025.1281
