Effect of drugs on the risk of injuries in children with attention deficit hyperactivity disorder: a prospective cohort study

Background Injuries represent the largest disease burden and most common cause of death in children. Attention deficit hyperactivity disorder (ADHD) is associated with increased mortality, with accidents being the most common cause of death in ADHD. However, it is not known whether pharmacological treatment has any modifying effect on the risk of injuries in children and adolescents with ADHD. Methods Using Danish national registers, we followed a cohort of 710 120 individuals, including 4557 individuals diagnosed with ADHD before age 10 years. Using a quasi-experimental, difference-in-difference design, we estimated the odds ratios (ORs) for injuries and the mean change in prevalence rates of injuries and emergency ward visits before and after treatment, with matched untreated children with ADHD at the same age serving as controls. Findings Children with ADHD were more likely to sustain injuries, compared with children without ADHD, at age 10 years (adjusted OR=1.29, 95% CI 1.22-1.37) and at age 12 years (adjusted OR=1.30, 1.23-1.37). From age 5 to 10 years, the prevalence of injuries in children with ADHD who were treated with ADHD drugs decreased from 19% to 14%, compared with a prevalence of about 17% in non-treated children with ADHD. This corresponded to an adjusted difference-in-difference reduction in prevalence of injuries at age 10 years of 31.5% (8.2-54.8) and 43.5% (18.1-69.0) at age 12 years due to treatment. Pharmacological treatment also reduced the prevalence of emergency ward visits at age 10 years (28.2%, 6.3-50.1) and age 12 years (45.7%, 25.8-65.7). Interpretation Children with ADHD had an increased risk of injuries compared with other children. Treatment with ADHD drugs reduced the risk of injuries by up to 43% and emergency ward visits by up to 45% in children with ADHD. Taken together with previous findings of accidents being the most common cause of death in individuals with ADHD, these results are of major public health importance. Funding The Lundbeck Foundation, the Danish Council for Independent Research, Centre For Integrated Register-based Research at Aarhus University, the Region of Southern Denmark Research Foundation, and Worzner's Foundation.