Causal Associations Between Immune Cell‐Specific Gene Expression and Major Depressive Disorder: A Single‐Cell Transcriptome‐Wide Mendelian Randomization Study

). Enrichment implicated Hedgehog signaling and folate metabolism. Drug repurposing highlighted metabolites targeting MTHFD1L and approved drugs targeting PTCH1 warranting further investigation. This study provides evidence for a genetically predicted causal relationship between immune cell-specific gene expression and MDD, which not only constructs a screening framework for candidate gene drug targets but also validates and finds potential drug targets.