The higher the household income, the lower the possibility of depression and anxiety disorder: evidence from a bidirectional Mendelian randomization study

Objectives: Observational studies have demonstrated that household income is associated with morbidity of mental disorders. However, a causal relationship between the two factors remains unclear. Therefore, we investigated the causal relationship between household income status and genetic liability of mental disorders using a bidirectional Mendelian randomization (MR) study.

Methods: This MR study included a large cohort of the European population from publicly available genome-wide association study datasets. A random-effects inverse-variance weighting model was used as the main standard, with MR-Egger regression, weighted median, and maximum likelihood estimations performed concurrently as supplements. Sensitivity analysis, consisting of heterogeneity and horizontal pleiotropy tests, was performed using Cochran's Q test, MR-Egger intercept, and MR-PRESSO tests to ensure the reliability of the conclusions.

Results: A higher household income tended to be associated with a lower risk of genetic liability for depression (odds ratio [OR]: 0.655, 95% confidence interval [CI] = 0.522-0.822, p < 0.001) and anxiety disorder (OR: 0.666, 95% CI = 0.526-0.843, p < 0.001). No associations were observed for schizophrenia (OR: 0.678, 95% CI = 0.460-1.000, p = 0.05), panic disorder (OR: 0.837, 95% CI = 0.445-1.577, p = 0.583), insomnia (OR: 1.051, 95% CI = 0.556-1.986, p = 0.877), obsessive-compulsive disorder (OR: 1.421, 95% CI = 0.778-2.596, p = 0.252), and bipolar disorder (OR: 1.126, 95% CI = 0.757-1.677, p = 0.556). A reverse MR study showed no reverse causal relationship between psychiatric disorders and household income. Sensitivity analysis verified the reliability of the results.

Conclusion: Our results revealed that the population with a higher household income tended to have a minor risk of genetic liability in depression and anxiety disorders.