Genetic overlap between depression and C-reactive protein levels: Evidence from a cross-trait analysis

Area of Science:

• Genetics
• Psychiatry
• Immunology

Background:

• Depression and inflammation, marked by elevated C-reactive protein (CRP), show consistent association.
• The underlying genetic mechanisms connecting depression and CRP levels are not well understood.

Purpose of the Study:

• To identify shared genetic loci (pleiotropic loci) between depression and CRP levels.
• To investigate the directionality of genetic effects and explore causal relationships, including the role of body mass index (BMI).

Main Methods:

• Integrated genome-wide association study (GWAS) data for depression and CRP.
• Utilized cross-trait analysis, functional annotation, gene set enrichment, colocalization, and Mendelian Randomization (MR).
• Stratified genetic variants by effect direction (concordant vs. discordant) and adjusted for BMI in MR analyses.

Main Results:

• Identified 9 novel genetic loci associated with both depression and CRP levels.
• Concordant loci implicated immune and inflammatory genes; discordant loci linked to metabolic pathways (e.g., lipid regulation).
• Mendelian Randomization strongly suggested BMI mediates a causal link from genetic depression liability to CRP levels.

Conclusions:

• Shared genetic factors contribute to the depression-CRP association, with distinct pathways for concordant and discordant effects.
• The direction of genetic effects is crucial for understanding the overlap between depression and inflammation.
• Body mass index (BMI) is a significant factor in the causal pathway linking depression to systemic inflammation.