Polygenic risk score
Schizophrenia
ICD-11 6A20 · Psychotic disorders
The schizophrenia polygenic risk score is among the most well-powered in psychiatric genetics — hundreds of genome-wide significant loci and roughly 9% variance explained in liability. It describes population-level risk architecture, not individual destiny.
Schizophrenia polygenic risk scores achieve among the strongest predictive performance in psychiatric genetics — explaining ~9% of variance in liability — yet a high score remains a probabilistic signal, not a diagnosis.
At a glance
Schizophrenia is the most heritable common psychiatric condition by twin studies. The 2022 PGC GWAS is the field's reference dataset, identifying 287 distinct genomic loci.
Schizophrenia is a severe, low-prevalence (~1%) psychiatric condition characterized by psychosis, disorganized thinking, and functional decline. Twin studies consistently estimate heritability around 70-80%. The 2022 PGC GWAS (Trubetskoy et al., Nature) analyzed ~76,000 cases and 244,000 controls and identified 287 genome-wide significant loci — by far the largest psychiatric GWAS for any condition by loci count.
What the GWAS actually found
The Trubetskoy et al. 2022 meta-analysis (Nature) combined 76,755 schizophrenia cases and 243,649 controls, identifying 287 distinct genomic loci reaching genome-wide significance. Top-hit genes include GRIN2A (a glutamate receptor subunit) and SP4 (a transcription factor with neurodevelopmental roles).
Twin-study heritability estimates for schizophrenia sit at roughly 0.60–0.80. The high SNP-based and twin-based heritability, combined with a large case cohort, make schizophrenia one of the best-powered psychiatric PRS targets — though the gap between statistical power and clinical utility remains wide.
Full citation: Trubetskoy V, et al. (2022). Mapping genomic loci implicates genes and synaptic biology in schizophrenia. Nature 604:502-508. PMID: 35396580..
How to read your percentile
Below 25th
Lower common-variant liability than most of the reference cohort. Does not rule out schizophrenia — CNVs and environmental exposures are independent risk factors.
25th–75th
Typical range. Your score sits near the population average; schizophrenia remains rare (~1% lifetime prevalence).
Above 75th
Elevated common-variant liability. This places you in a higher-risk tail of the PRS distribution, but absolute risk remains low and environmental exposures (cannabis use, urban upbringing, trauma) interact with genetic liability.
What this does not tell you
A schizophrenia PRS cannot diagnose schizophrenia, predict conversion from prodromal to psychotic states, or identify which antipsychotic will work. It also cannot distinguish schizophrenia from related psychotic-spectrum phenotypes — there is substantial genetic overlap with bipolar disorder and related conditions.
Rare highly penetrant CNVs (e.g., 22q11.2 deletion, 15q13.3 deletion, 16p11.2 duplication) confer much larger schizophrenia risk than common variants and are invisible to a PRS built from SNP array data. Cross-ancestry transportability is reduced: most GWAS data is European-ancestry, and East Asian and African cohorts show different allele frequencies and effect-size patterns at key loci.
Related traits
Schizophrenia shares common-variant architecture with several other psychiatric conditions. Genetic correlations (rg) reflect how often the same variants move risk for both traits in the same direction.
Frequently asked questions
Is schizophrenia 'genetic'?
Schizophrenia has strong genetic contributions — twin heritability around 0.60–0.80 — but genetic liability is polygenic (thousands of small-effect common variants) and probabilistic. Most people with elevated PRS will never develop schizophrenia, and rare CNVs confer much higher individual risk than common-variant PRS.
Does this score predict who will develop psychosis?
No. PRS is a population-level statistic. Even in the top percentile, most individuals will not develop schizophrenia. Clinical prediction of first-episode psychosis remains the domain of prodromal symptom assessment and clinical interviews, not genetics.
How does this compare to a 22q11.2 deletion test?
A 22q11.2 deletion is a rare copy-number variant conferring ~25–30× increased schizophrenia risk per carrier — orders of magnitude larger than any common-variant PRS effect. CNV testing requires dedicated clinical-grade assays (array CGH, targeted MLPA). A common-variant PRS from SNP array data cannot detect CNVs.
Why is the schizophrenia PRS more accurate than depression's?
Tighter case definitions, higher per-variant effect sizes, and large case cohorts combine to give the schizophrenia PRS ~9% variance explained — one of the best in psychiatric genetics. The depression PRS, despite a larger total cohort, captures only ~3% because the underlying architecture is more diffuse and the diagnostic construct more heterogeneous.
Sources
- Trubetskoy et al. 2022, Nature 604:502–508. doi.org/10.1038/s41586-022-04434-5
- PGC Schizophrenia Working Group. pgc.unc.edu/for-researchers/working-groups/schizophrenia-workgroup/
- Sullivan et al. 2012 — Family history & genetics of schizophrenia. doi.org/10.1038/nrg3240
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