Association between depression and COPD: results from the NHANES 2013-2018 and a bidirectional Mendelian randomization analysis

Background: Observational studies showed a bidirectional association between depression and chronic obstructive pulmonary disease (COPD). However, it is unclear whether the observed association is causal. Thus we estimated the relationship using observational studies combined with bidirectional Mendelian randomization [MR].Materials and methods: The study included 9977 participants from the 2013-2018 National Health and Nutrition Examination Survey and used weighted logistic regression analysis to assess the association between depression and COPD, followed by a bidirectional Mendelian randomization analysis to verify their causality.Results: Adjusted-weighted logistic regression in observational studies showed a significant association between COPD and mild depression (OR (95% CI): 1.81 (1.30, 2.52), P = 0.002) and COPD and depression (OR (95% CI): 1.93 (1.49, 2.50), P < 0.001). MR suggested depression may play a causal role in COPD risk (OR (95% CI): 1.45 (1.32, 1.60), P < 0.001), but more evidence for reverse causation is lacking (reverse MR OR (95% CI): 1.03 (0.99, 1.07), P = 0.151).Conclusion: In conclusion, our study found depression may play a potential causal role in the morbidity of COPD suggesting depression might be the etiology of COPD. This finding needs to be validated in further prospective cohort studies with large sample sizes and adequate follow-up time.