Stimulant treatment and injury among children with attention deficit hyperactivity disorder: an application of the self-controlled case series study design

Objective The aim of the present work was to assess the short-term effects of stimulant medication use on risk of injury among children diagnosed as having attention deficit hyperactivity disorder (ADHD). Methods The study group for this self-controlled case series study was children aged 1-18 years old diagnosed as having ADHD who experienced an incident medically-attended injury event and received at least one prescription for stimulant medication between 1993 and 2008 (n=328), identified from The Health Improvement Network primary care database from the UK. Conditional Poisson regression was used to estimate incident rate ratios (IRR) and 95% CIs for injury comparing periods of time exposed to stimulant medication to unexposed periods. Results Among children with ADHD prescribed stimulant medication, the rate of medically-attended injury was decreased during periods of stimulant medication use as compared to unexposed periods (IRR 0.68, 95% CI 0.50 to 0.91). There was evidence of a protective association among males and among children aged 10-14 years. This effect did not change over time on treatment. Conclusions Stimulant medication use may decrease the risk of injury among children treated for ADHD, although unmeasured time varying confounding may be an alternative explanation. Injury risk may be considered during the decision-making process with regard to medication continuation among children with ADHD.