Relationships of Antidepressant Medication With Its Various Factors Including Nitrogen Dioxides Seasonality: Machine Learning Analysis Using National Health Insurance Data

Objective This study employs machine learning and population-based data to examine major factors of antidepressant medication including nitrogen dioxides (NO₂) seasonality. Methods Retrospective cohort data came from Korea National Health Insurance Service claims data for 43,251 participants with the age of 15–79 years, residence in the same districts of Seoul and no history of antidepressant medication during 2002–2012. The dependent variable was antidepressant-free months during 2013–2015 and the 103 independent variables for 2012 or 2015 were considered, e.g., particulate matter less than 2.5 micrometer in diameter (PM_2.5), PM₁₀, NO₂, ozone (O₃), sulphur dioxide (SO₂) and carbon monoxide (CO) in each of 12 months in 2015. Results It was found that the Cox hazard ratios of NO₂ were statistically significant and registered values larger than 10 for every three months: March, June–July, October, and December. Based on random forest variable importance and Cox hazard ratios in brackets, in-deed, the top 20 factors of antidepressant medication included age (0.0041 [1.69–2.25]), migraine and sleep disorder (0.0029 [1.82]), liver disease (0.0017 [1.33–1.34]), exercise (0.0014), thyroid disease (0.0013), cardiovascular disease (0.0013 [1.20]), asthma (0.0008 [1.19–1.20]), September NO₂ (0.0008 [0.01]), alcohol consumption (0.0008 [1.31–1.32]), gender-woman (0.0007 [1.80–1.81]), July NO₂ (0.0007 [14.93]), July PM₁₀ (0.0007), the proportion of the married (0.0005), January PM_2.5 (0.0004), September PM_2.5 (0.0004), chronic obstruc-tive pulmonary disease (0.0004), economic satisfaction (0.0004), January PM₁₀ (0.0003), residents in welfare facilities per 1,000 (0.0003 [0.97]), and October NO₂ (0.0003). Conclusion Antidepressant medication has strong associations with neighborhood conditions including NO₂ seasonality and welfare support.