Objective: There is growing evidence that suggests a potential association between particulate matter (PM) and suicide. However, it is unclear that PM exposure and suicide death among major depressive disorder (MDD) patients, a high-risk group for suicide.Methods: We investigated the risk of suicide among 1,046,169 newly-diagnosed MDD patients from 2004 to 2015 within the Korean National Health Insurance Service (NHIS) database. We identified 3,372 suicide cases from January 1, 2015, to

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... 31, 2017, within the death statistics database of the Korean National Statistical Office. PMs with diameter less than 2.5 μm (PM2.5), less than 10 μm (PM10), and 2.5 μm to 10 μm (PM2.5-10) were considered, which were provided from the National Ambient Air Monitoring System in South Korea. Time-stratified case-crossover analysis was performed to investigate the association of particulate matter exposure to suicide events.Results: The risk of suicide was significantly high upon the high level of exposure to PM2.5-10, PM10 on lag 1 (p for trend = 0.044, 0.035, respectively). A similar association was observed in the multi-day lag model (lag 0-3). Increasing exposure to PM 2.5 was not associated with increased suicide risk.Conclusions: Short-term exposure to a high level of PM2.5-10 and PM10 was associated with an elevated risk for suicide among MDD patients, while PM2.5 did not. There is a clear dose-response relationship between short-term coarse particle exposures with suicide death among Major Depressive Disorder patients. This result will be used as an essential basis for consideration when establishing an air pollution alarm system and implementing a suicide prevention program for reducing adverse health outcomes by PM.