To understand whether injury risk is reduced during treatment of attention-deficit/hyperactivity disorder (ADHD), researchers from the University of North Carolina and the University of Pennsylvania retrospectively assessed data from general practices (GP) in the United Kingdom. Information was abstracted on children under 19 years of age with ADHD who had ever been treated with stimulant medication, applying a self-controlled design in which each child served as his/ her own control. Every medically-attended injury that occurred in a study child was classified as having occurred either during a treated or an untreated period. A “treated period” was defined as starting on the day a stimulant was prescribed and extending through the end of the period for which medication was supplied, plus a 30-day grace period. The grace period was used to try to minimize misclassification of a period as untreated when a child was actually still using medication. Because injury risk for a given individual can vary with age and season, researchers controlled for these variables in the analysis. The incident rate ratio (IRR) for injuries occurring during a treated period was compared to injuries occurring during an untreated period.

Of 4,234 children diagnosed with ADHD and treated at least once with stimulant medication, 328 had an injury attended medically at the GP, emergency department, or hospital. Most (86.9%) were male, and the mean age of ADHD diagnosis was 9.7 years. The mean observation period was 5.9 years per child. Almost all study participants (98.5%) were treated with methylphenidate. The leading types of incident injuries were fractures, head injuries, sprains/strains, contusions, and superficial skin injuries. The adjusted IRR for injury during treated periods compared to injury during untreated periods was 0.68 (95% CI, 0.50–0.91). Subgroup analysis showed the effect of treatment was most statistically convincing among males and children aged 10 to 14 years.

The authors conclude that periods of stimulant medication use are associated with lower risk of injury among children treated for ADHD. They caution that other factors not measured for individuals in this study might provide alternative explanations for their findings.