Attention-deficit/Hyperactivity Disorder (ADHD) pharmacological treatment and its effect on accident and emergency admission due to injury: a self-controlled case-series study

Abstract

BACKGROUND: Attention-Deficit/Hyperactivity Disorder (ADHD) patients have a higher tendency to sustain trauma requiring Accident & Emergency Department (ED) visits. Evidence that ADHD patients on pharmacotherapy tend to have a lower ED admission rate compared to those without medication is limited. OBJECTIVES: To investigate the association between ADHD drug treatment and Accident & Emergency Department (ED) admission from injuries. METHODS: Design: Self-controlled case series study. SETTING: Patients aged 6 to 19 with at least one prescription of Methylphenidate (MPH) and at least one ED admission from injury in 2001 to 2013 were identified (n = 5178) using Hong Kong Population-based electronic medical records in the Clinical Data Analysis & Reporting System (CDARS). Main Outcome Measure: Relative incidence of ED admission from injuries comparing exposed and non-exposed periods was estimated. Individual observation period commenced latest 1st January, 2001 or on patient’s 6th birthday, and ended earliest 31st December, 2013, on the patient’s 20th birthday or the date of registered death. The Incidence Rate Ratios (IRRs) and the corresponding 95% confidence intervals were calculated using conditional Poisson regression. RESULTS: Among patients prescribed MPH, the rate of ED admission from injuries was decreased during exposed periods compared to non-exposed periods (IRR = 0.91, 95%CI 0.86 to 0.97). Similar results were observed if only the first injury episode was counted (IRR = 0.88, 95%CI 0.81 to 0.96). Sensitivity Analysis was conducted by adding 1 to 10 weeks after the end of an exposed period which gave consistent results. CONCLUSIONS: This study supports the hypothesis that MPH can reduce the risk of injury-related ED admission in children and adolescents. Long term MPH treatment prevents injuries in this group of high-risk patients and this potential benefit should be considered in clinical practice.