Background. Atopic dermatitis (AD) has long been hypothesized to be associated with risk of depression and suicide, but the causal relationship between them is still unclear. Objective. To evaluate the causality between AD, depression, and suicide using a Mendelian randomization (MR) approach. Method. We extracted summary-level data for AD, major depression, and suicidal ideation or attempt from published, nonoverlapping genome-wide association studies (GWAS). Inverse variance-weighted (IVW) analysis was used as the primary analysis. Alternate methods, including weighted median, MR Egger, MR pleiotropy residual sum and outlier, weighted mode, and leave-out analysis, were performed to assess pleiotropy. Results. 13 SNPs (13,287 cases and 41,345 controls) were selected as instrumental variables (IVs). The IVW analysis indicated a statistically significant but small causal effect of AD on major depression (OR=1.027, 95% CI 1.004-1.050; p=0.020). No significant evidence was observed for a causal effect of AD on suicide. No significant effect of pleiotropy was found. Conclusion. AD has a significant but small effect on major depression, but not on suicide.