Is Depression Genetic? What DNA Says About Schizophrenia, Bipolar, and Anxiety
Psychiatric conditions are 35–85% heritable, with 200+ risk loci for schizophrenia alone. But polygenic scores can’t diagnose mental illness. Here’s what genetics actually reveals.
Category: Research · By GenomeNarrator Team · · 7 min read
Psychiatric conditions are among the most heritable common conditions in medicine. Twin studies estimate heritability at 60–80% for schizophrenia, 60–85% for bipolar disorder, and 35–50% for major depression. Yet the genetics underlying these conditions are extraordinarily complex.
The polygenicity of psychiatric conditions
Unlike many physical conditions where a single gene variant can be highly informative, psychiatric conditions involve thousands of variants each with tiny individual effects. The largest GWAS for schizophrenia (PGC3, n>300,000) identified over 200 genome-wide significant loci, and these explained only a fraction of the total genetic variance.
Shared genetic architecture
One of the most striking findings in psychiatric genetics is that the major conditions (schizophrenia, bipolar disorder, depression, ADHD, and autism) share substantial genetic overlap. Many variants increase risk for multiple conditions simultaneously, which helps explain why these conditions often co-occur in individuals and families.
The copy number variant exception
For schizophrenia specifically, rare copy number variants (CNVs), large deletions or duplications of chromosomal segments, can have large individual effects. The 22q11.2 deletion is associated with a 20–30% lifetime risk of schizophrenia. These are detectable in genomic data and GenomeNarrator screens for known pathogenic CNVs.
What we report and how
GenomeNarrator includes psychiatric polygenic risk scores with explicit caveats about their current clinical utility. These scores are most useful for research and personal education rather than clinical decision-making at this stage. We do not use any genetic finding to suggest or imply a diagnosis.
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