Major depressive disorder and cardiometabolic diseases: a bidirectional Mendelian randomisation study

Observational studies have shown a bidirectional association between major depressive disorder (MDD) and cardiometabolic diseases. We conducted a two-sample bidirectional Mendelian randomisation (MR) study to assess the causal associations of MDD with type 2 diabetes, coronary artery disease (CAD) and heart failure and vice versa.We extracted summary-level data for MDD, type 2 diabetes, CAD and heart failure from corresponding published large genome-wide association studies of individuals mainly of European-descent. In total, 96 SNPs for MDD, 202 SNPs for type 2 diabetes, 44 SNPs for CAD and 12 SNPs for heart failure were proposed as instrumental variables at the genome-wide significance level (p < 5 × 10-8). The random-effects inverse-variance weighted method was used for the main analyses.Genetic liability to MDD was significantly associated with type 2 diabetes and CAD at the Bonferroni-corrected significance level. The ORs of type 2 diabetes and CAD were respectively 1.26 (95% CI 1.10, 1.43; p = 6 × 10-4) and 1.16 (95% CI 1.05, 1.29; p = 0.0047) per one-unit increase in loge odds of MDD. There was a suggestive association between MDD and heart failure (OR 1.11 [95% CI 1.01, 1.21]; p = 0.033). We found limited evidence supporting causal effects of cardiometabolic diseases on MDD risk in the reverse MR analyses.The present study strengthened the evidence that MDD is a potential risk factor for type 2 diabetes and CAD. Whether MDD is causally related to heart failure needs further study.All data included in this study were uploaded as supplements and are also publicly available through published GWASs and open GWAS datasets (UK Biobank, 23andMe and Psychiatric Genomics: https://datashare.is.ed.ac.uk/handle/10283/3203; DIAGRAM: http://diagram-consortium.org/downloads.html; CARDIoGRAMplusCD4: www.cardiogramplusc4d.org/; HERMES: http://www.kp4cd.org/datasets/mi). Graphical abstract.