Asthma and self-harm: a population-based cohort study in Taiwan.

OBJECTIVE Few studies have investigated the relationship between asthma and suicidality-related outcomes in the world. We sought to investigate the association between asthma and risk of non-fatal self-harm in a large national sample. METHODS Cases aged 10years and over were identified from Taiwan's National Health Insurance Research Database with a new primary diagnosis of asthma (ICD-9:493) between 2000 and 2008. Case status required the presence of any inpatient diagnosis of asthma and/or at least two recorded diagnoses and 1year duration of asthma in outpatient services. These 27,781 cases were compared to 138,905 sex- and age-matched controls and both groups were followed until end of 2008 for instances of self-harm, defined as ICD-9 codes E950-E959 (self-harm causes) and E980-E989 (undetermined causes). Competing risk adjusted Cox regression analyses were applied, adjusting for sex, age, residence (urban/rural), insurance premium, episode of psychiatric disease, montelukast, Charlson comorbidity index and mortality. RESULTS Of the 166,686 subjects, 445 carried out self-harm during a mean (SD) follow-up period of 5.84 (2.35) years. Asthma (hazard ratio=1.70, 95% CI: 1.35-2.14), age, residence, episode of psychiatric disease and Charlson comorbidity index were independent risks on self-harm in the fully adjusted model. CONCLUSIONS Asthma was associated with increased risk of self-harm in this population, independent of a number of potential confounding factors including montelukast use. This reinforces the need to consider mental health in routine asthma care, and to consider asthma as a potentially important stressor in people with comorbid mental disorder.