Importance: Few studies have investigated levels of mortality in patients with attention-deficit/hyperactivity disorder (ADHD), and findings have been inconsistent and lacking information on specific causes of deaths. Objective: To investigate the association between ADHD and causes of death in Taiwan. Design, Setting, and Participants: A nationwide population-based cohort study was conducted using a cross-national Taiwanese registry. The ADHD group comprised 275980 individuals aged 4 to 44 years with a new diagnosis between January 1, 2000, and December 31, 2012. All individuals with ADHD were compared with 1931860 sex- and age-matched controls without ADHD. Exposures: The association between ADHD and mortality was analyzed using a Cox regression model that controlled for sex, age, residence, insurance premium, outpatient visits, congenital anomaly, intellectual disability, depression disorder, autism, substance use disorder, conduct disorder, and oppositional defiant disorder. The analysis of suicide, unintentional injury, homicide, and natural-cause mortality was performed by a competing risk adjusted Cox regression controlling for other causes of mortality and potential confounding factors. Main Outcomes and Measures: Data on mortality from all causes, suicide, unintentional injury, homicide, and natural causes collected from a national mortality database. Results: There were 275980 individuals with ADHD and 1931860 comparison individuals without ADHD in this study. Sex and age at index date were matched. The mean (SD) age was 9.61 (5.74) years for both groups. Most of the participants were male (209406 in the ADHD group; 1465842 in the non-ADHD group; 75.88% for both groups). A total of 4321 participants from both cohorts died during the follow-up period (15.1 million person-years), including 727 (0.26%) from the ADHD group and 3594 (0.19%) from the non-ADHD group. Of those who died, 546 (75.1%) in the ADHD group and 2852 (79.4%) in the non-ADHD group were male. After adjusting for potential confounders, compared with the non-ADHD group, patients with ADHD showed higher overall mortality (adjusted hazard ratio, 1.07; 95% CI, 1.00-1.17) and higher injury-cause mortality from suicide (adjusted hazard ratio, 2.09; 95% CI, 1.62-2.71), unintentional injury (adjusted hazard ratio, 1.30; 95% CI, 1.10-1.52), and homicide (adjusted hazard ratio, 2.00; 95% CI, 1.09-3.68). No increased risk of natural-cause mortality was observed after adjustment. Conclusions and Relevance: In this study, ADHD was associated with higher injury-cause mortality, particularly that due to suicide, unintentional injury, and homicide. Although the risk of injury mortality was significantly higher in patients with ADHD than in the non-ADHD group, the absolute risk of mortality was low.
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