www.e-epih.org | 1 INTRODUCTION Atopic dermatitis (AD) is an infammation of the skin accom- panied by itchiness, and numerous studies conducted throughout the world have reported AD to be associated with depression [1- 5]. A study conducted in Taiwan among adolescents and adults with AD found a positive association between AD and depression in both groups, although the risk of AD for depression was higher among adults than among adolescents [1]. Furthermore, a study of 257 AD patients in the US found a signifcant association be- tween the severity of AD and depression [6]. Studies reporting an association between AD and depression in Korea have also been published [7-9]. A study using Korea Community Health Survey (KCHS) data from 2008 to 2013 presented a 1.33 times (95% con- fdence interval [CI], 1.02 to 1.74) higher risk of depression in AD patients than in non-AD patients [9]. Furthermore, adolescents with AD were 1.27 times more likely to experience depression symptoms [7]. Te prevalence of both depression and AD is in- creasing in Korea [10,11]; therefore estimating the risk of AD for OBJECTIVES: Numerous studies have reported associations between atopic dermatitis (AD) and depression, but the causal re- lationship between the 2 diseases has not been established. Terefore, this study used the propensity score method to investigate whether there was a positive causal efect of AD on depression in 16 regions (cities and provinces) in Korea. METHODS: Te study analyzed 16 regions (cities and provinces) in Korea, using data obtained from the Korea Community Health Survey for the years 2010-2013. Propensity score matching was used to estimate the causal infuence of AD on depression in Korea. RESULTS: Afer propensity score matching, the standardized diference for each covariate among the 16 regions (cities and prov- inces) was less than 1, indicating a balance between the case and control groups. At the national level, those diagnosed with AD had a 2.31 times higher risk for being diagnosed with depression than those who had not been diagnosed with AD. In particular, the risk was highest in North Jeolla Province (odds ratio [OR], 4.87; 95% confdence interval [CI], 2.28 to 10.43) and lowest in Gwangju (OR, 1.82; 95% CI, 0.87 to 3.79), and the OR for Seoul was 2.23 (95% CI, 1.66 to 2.99). CONCLUSIONS: Tis study provides insights into how causal inferences can be derived from observational studies, through an analysis of Korea Community Health Survey data. Furthermore, the study results have implications for region-specifc guidelines for preventive health policies targeting depression. KEY WORDS: Atopic dermatitis, Depression, Epidemiology, Propensity score Open Access ORIGINAL ARTICLE Volume: 40, Article ID: e2018059, 8 pages https://doi.org/10.4178/epih.e2018059 Estimating causal associations of atopic dermatitis with depression using the propensity score method: an analysis of Korea Community Health Survey data, 2010-2013 Hayon Michelle Choi, Dahye Kim, Whanhee Lee, Ho Kim Graduate School of Public Health, Seoul National University, Seoul, Korea Correspondence: Ho Kim Graduate School of Public Health, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826, Korea E-mail: hokim@snu.ac.kr Received: Sep 18, 2018 / Accepted: Nov 29, 2018 / Published: Nov 29, 2018 This article is available from: http://e-epih.org/ This is an open-access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 2018, Korean Society of Epidemiology