Relationship of Depression and Asthma: A Observational and Mendelian randomization study

Background Both depression and asthma have a significant impact on the quality of life for individuals. Studies have shown that patients with depression often experience comorbid asthma; however, the precise relationship between these two conditions remains unclear. The objective of this study is to investigate the causal relationship between depression and asthma. Methods In a cross-sectional study, we utilized data from the National Health and Nutrition Examination Survey (NHANES) 2009-2014 and employed logistic regression to assess the correlation between depression and asthma. In the subsequent Mendelian randomization (MR) analysis, we selected single nucleotide polymorphisms (SNPs) closely linked to both depression and asthma as instrumental variables, based on summary data from genome-wide association studies (GWAS). The inverse variance weighted method (IVW) was then applied to ascertain the causal relationship between depression and asthma. Results Based on the results of the cross-sectional study, it was found that the status of depression was significantly associated with a higher risk of asthma (OR = 2.15, 95%CI = 1.79 ∼ 2.59, P < 0.001). Furthermore, in the MR analysis, a causal relationship was further identified between depression, severe depression, and the increased incidence of asthma (OR = 1.11, 95%CI = 1.05 ∼ 1.18, P < 0.001), (OR = 1.01, 95%CI = 1.01 ∼ 1.02, P < 0.001); the results of the reverse MR analysis indicated no causal relationship between asthma and the increased incidence of depression and severe depression (OR = 1.01, 95%CI: 0.99 ∼ 1.03, P = 0.50), (OR = 1.07, 95%CI: 0.82 ∼ 1.40, P = 0.64). Conclusion This study has revealed a causal relationship between depression and an increased risk of developing asthma, offering new insights for the clinical intervention of both asthma and depression.