Dosage of methylphenidate and traumatic brain injury in ADHD: a population-based study in Taiwan.

Preventive effect of stimulants on the risk of brain injuries had been reported. The aim of this study is to determine the extent to which methylphenidate (MPH) prescription moderates the risk of traumatic brain injuries (TBI) in individuals with attention-deficit/hyperactivity disorder (ADHD). Individuals with a recent diagnosis of ADHD between January 1997 and December 2013 (n = 163,618) were identified from Taiwan's National Health Insurance Research Database. A total of 124,438 adolescents and children with ADHD and without prior TBI diagnoses were included and evaluated for subsequent TBI. Methylphenidate prescription duration was subgrouped by the annual average cumulative defined daily dose (DDD): 0, >0 to ≤28, > 28 to ≤84, and >84. We identified 11,463 diagnoses of TBI among 124,438 adolescents and children with ADHD. A Cox regression model was used to investigate whether MPH prescription influenced the risk for TBI after adjusting for sex, age, level of urbanization, seizure, autism and sedative-anxiolytics use. A reduced TBI incidence was observed with MPH prescription DDDs > 84. The protective effect of MPH against TBI persisted after adjusting for confounding factors [hazard ratio (HR) = 0.49; 95% confidence interval (CI): 0.47-0.51]. There was also statistically significant difference in risk for TBI in subjects receiving > 0 to ≤28 or >28 to ≤84 DDDs of MPH treatment (HR = 0.88, 95% CI = 0.83-0.92; HR = 0.76, 95% CI = 0.72-0.80, respectively) when compared with subjects not receiving treatment with MPH. Treatment with MPH for greater than 84 DDDs reduced the risk for TBI among children with ADHD.