Background: Previous researches have demonstrated a connection between psychiatric disorders and cardiovascular diseases (CVDs), but the cause-and-effect relationship is still unclear. To that goal, the mendelian randomization (MR) method was used to study the causal link between psychiatric disorders and CVDs.

Methods: Genome-wide association studies (GWAS) data were collected for four CVDs, including coronary artery disease (n = 547,261), atrial fibrillation (n = 537,409), heart failure (n = 977,323) and ischemic stroke (n = 440,328). Summary data for four psychiatric disorders, including bipolar disorder (n = 51,710), major depressive disorder (n = 480,359), schizophrenia (n = 127,906) and attention deficit hyperactivity disorder (n = 55,374), came from the Psychiatric Genomics Consortium (PGC). All participants were European. The IVW method was mainly used, and the reliability of the results was increased using sensitivity analyses such as MR-Egger, Cochrane's Q test, MR-PRESSO and leave-one-out.

Results: MR revealed that the attention deficit hyperactivity disorder was linked to an increased risk of atrial fibrillation (OR, 1.085; 95% CI, 1.021-1.153; P = 0.008), heart failure (OR, 1.117; 95% CI, 1.044-1.195; P = 0.001), and ischemic stroke (OR, 1.146; 95% CI, 1.052-1.248; P = 0.002). The schizophrenia was linked to an increased risk of heart failure (OR, 1.035; 95% CI, 1.006-1.066; P = 0.017), but was found to be suggestively inverse associated with coronary artery disease (OR, 0.969; 95% CI, 0.941-0.997; P = 0.03). The major depressive disorder was associated with higher odds of coronary artery disease (OR, 1.109; 95% CI, 1.018-1.208; P = 0.018), while the bipolar disorder was linked to a reduced incidence of coronary artery disease (OR, 0.894; 95% CI, 0.831-0.961; P = 0.002) and heart failure (OR, 0.889; 95% CI, 0.829-0.955; P = 0.001). There were no clear relationships between other psychiatric disorders and CVDs.

Conclusion: The results provide genetic proof of a possible causal relationship between psychiatric disorders and CVDs. These results imply that psychiatric disorders may be the cause of some CVDs, and that some abnormal mental states may increase or reduce the likelihood of CVDs, providing guidance for the CVDs prevention.