The Causal Relationship Between Atopic Dermatitis and Multiple Sclerosis: A Two‐Sample Mendelian Randomization Study

Background Existing population‐based cohort studies have been devoted to find the correlation between atopic dermatitis (AD) and autoimmune diseases including multiple sclerosis (MS). However, whether there is a causal relationship between AD and MS remains elusive. Objective The study aims to assess the causal links between AD and MS. Methods We utilized two‐sample Mendelian randomization (MR) analysis to investigate the causal links between AD and MS. The data for AD were obtained from a published paper. And the instrumental variables of MS are acquired from FinnGen consortium. They were selected under the three core assumptions of MR analysis. To investigate the causal relationship, we employed MR‐Egger, weighted median, inverse variance weighted (IVW), weighted mode, and simple mode for MR analysis. Sensitivity tests were performed including Cochran’s Q test to assess heterogeneity, the MR‐Egger intercept test was used to assess horizontal pleiotropy, and the leave‐one‐out test was used to assess stability. Results The IVW results validated a causal link between AD and MS (OR = 1.376, 95% CI: 1.063–1.781, and p = 0.015). In terms of the sensitivity analyses, Cochran’s Q test showed that there was both no significant heterogeneity (IVW p = 0.628 and MR‐Egger p = 0.799) and horizontal pleiotropy ( p = 0.071). And the leave‐one‐out sensitivity test showed that there was no IV dominating the overall MR results. Conclusion The MR analysis sheds lights on the causal role of AD on MS. AD is associated with an elevated risk of MS.