: When a gene affects multiple traits independently, potentially biasing the causal estimate.

MR uses genetic variants as "natural experiments" to determine if an exposure (like high blood pressure) truly causes a disease (like stroke), rather than just being associated with it. ⚖️ The Three Pillars of MR Validity

: Typically single nucleotide polymorphisms (SNPs) identified through Genome-Wide Association Studies (GWAS) . Data Types :