The impact of sitting time and physical activity on major depressive disorder in South Korean adults: A cross-sectional study

Background: Previous studies have examined associations between sitting time and negative health outcomes and mental health. However, the relationship between overall sitting time and major depressive disorder (MDD) in South Korea has not been studied. This study examined the association between MDD and overall sitting time and physical activity in South Koreans. Methods: Data from the sixth Korean National Health and Nutrition Examination Survey (KNHANES), a cross-sectional, nationally representative survey, were analyzed. Total participants were 4145 in 2014. MDD was assessed using the Patient Health Questionnaire (PHQ-9). Participants' data regarding self-reported sitting time and physical activity were analyzed via multiple logistic regression. Results: Results showed that people who sat for 8-10 h (OR: 1.56, 95% CI: 1.15-2.11) or more than 10 h (OR: 1.71, 95% CI: 1.23-2.39) had increased risk of MDD compared to those who sat for less than 5 h a day. Subgroup analysis showed that the strongest effect of reported sitting time on risk of MDD was found in men with lower levels of physical activity who sat for 8 to 10 h (OR: 3.04, 95% CI: 1.15-8.01) or more than 10 h (OR: 3.43, 95% CI: 1.26-9.35). Level of physical activity was not an independent predictor for MDD. Conclusions: Sitting for long periods was associated with greater risk of MDD in South Korean adults. Reducing sitting time in people with MDD could help to prevent associated physical health problems and may improve mental health.