Minimal phenotyping yields genome-wide association signals of low specificity for major depression

Area of Science:

• Psychiatric Genetics
• Human Genomics
• Computational Biology

Background:

• Minimal phenotyping, using few self-reported items, is increasingly common in genome-wide association studies (GWAS).
• This approach is used for disease case identification, including for major depressive disorder (MDD).

Purpose of the Study:

• To investigate differences in genetic architecture between depression defined by minimal phenotyping and strictly defined major depressive disorder (MDD).
• To assess the impact of minimal phenotyping on the interpretation of genetic findings for MDD.

Main Methods:

• Comparison of genotype-derived heritability between minimal and strict phenotyping for MDD.
• Analysis of the proportion of the genome contributing to genetic liability.
• Evaluation of loci identified by GWAS using minimal phenotyping.
• Assessment of polygenic risk score (PRS) predictive power and specificity.

Main Results:

• Minimal phenotyping for MDD showed lower heritability than strict MDD definitions, not solely due to milder cases.
• A larger genomic proportion contributed to shared genetic liability with other conditions in minimal phenotyping.
• GWAS using minimal phenotyping identified loci not specific to MDD.
• Highly predictive PRS from minimal phenotyping were driven by sample size, not MDD specificity.

Conclusions:

• Reliance on minimal phenotyping may distort understanding of MDD's genetic architecture.
• This approach can hinder the identification of pathways specifically implicated in MDD.
• Future genetic studies should carefully consider phenotyping strategies for accurate MDD genetic insights.