In a groundbreaking synthesis published in the latest issue of Genomic Psychiatry, researchers have unveiled a detailed exploration of the complex genetic terrain underlying common epilepsies. Led by Dr. Olav B. Smeland of Oslo University Hospital and the University of Oslo, the comprehensive mini-review consolidates a decade’s worth of advances in molecular genetics, ranging from genome-wide association studies to whole-exome sequencing and sophisticated statistical modeling. This work reframes the understanding of epilepsy, not as a single disorder but as a multifaceted collection of neurological syndromes shaped by a polygenic architecture far richer than previously appreciated.
Epilepsy affects roughly 50 million people worldwide, presenting a spectrum of clinical manifestations that confound treatment and prognosis. While severe, monogenic epilepsies such as developmental and epileptic encephalopathies have been elucidated through the identification of over a thousand implicated genes, the genetics of common epilepsies has remained elusive. This delay stems from the intricate polygenic nature of these disorders, where thousands of genetic variants, each with modest effect sizes, collectively influence disease risk and subtype specificity.
The pioneering work draws its historical roots from twin studies conducted nearly a century ago, which first highlighted disparities in concordance rates between monozygotic and dizygotic twins. These studies showcased stark contrasts in inheritance patterns, especially when dissecting epilepsy into subtypes: genetic generalized epilepsy exhibited monozygotic concordance as high as 77%, remarkably different from focal epilepsy’s 40%. This discrepancy raised fundamental questions about the genetic heterogeneity inherent to different epilepsy phenotypes.
Modern genetic epidemiology quantifies heritability through SNP-heritability metrics, which capture the proportion of phenotypic variance attributable to common single nucleotide polymorphisms (SNPs). Intriguingly, genetic generalized epilepsy displays SNP-heritability estimates approximately threefold greater than those of focal epilepsy, with some subtypes like juvenile myoclonic epilepsy demonstrating even higher values. This underscores the critical importance of diagnostic precision in genetic studies and hints at divergent pathophysiological mechanisms underpinning epilepsy subtypes.
Complementing the polygenic backdrop, the review emphasizes the significant but more sporadic role of rare variants in epilepsy risk. Copy number variant analyses involving over 13,000 cases point to an elevated genomic burden across epilepsy types, with genetic generalized epilepsy showing a striking enrichment at loci such as 15q13.3—a deletion that confers an extraordinarily high odds ratio of 36.04. Although this massive effect impacts only a small subset of patients, it exemplifies how rare, high-impact mutations coexist alongside widespread polygenic influences.
Equally compelling is the convergence observed between rare variant and common variant signals. Whole-exome sequencing has repeatedly implicated ultrarare, protein-truncating mutations in genes encoding components of the GATOR1 complex, a key regulator of the mTORC1 signaling pathway, as pivotal risk factors for non-acquired focal epilepsy. Genes such as DEPDC5, NPRL3, SCN1A, and SCN8A emerge repeatedly across diverse analyses, suggesting that common and rare variant burdens may channel through shared biological networks linked to ion channel function, synaptic transmission, and excitatory-inhibitory balance.
Genome-wide association studies (GWAS) have further expanded this landscape. The largest epilepsy GWAS to date, encompassing close to 30,000 cases and over 52,000 controls, identified 26 genome-wide significant loci predominantly linked to genetic generalized epilepsy. Notably, despite a higher number of focal epilepsy cases in the cohort, this subtype yielded no genome-wide significant associations, emphasizing fundamental differences in the genetic architectures of epilepsy forms. Dr. Smeland remarks that the relatively favorable heritability-to-polygenicity ratio in generalized epilepsies enables more powerful gene discovery with modestly increased sample sizes compared to similarly complex neurological disorders.
The integration of monogenic and polygenic genetic data uncovers a remarkable overlap of candidate genes across epilepsy forms. Ten of the prioritized genes at the 26 identified loci have been previously established in monogenic epilepsies. These encompass critical ion channel subunits (SCN8A, SCN1A, CACNA1I, KCNN2) and neurotransmitter receptor components (GABRA2, GRIK1), highlighting shared pathophysiological pathways. This convergence challenges the conventional dichotomy between rare, high-penetrance mutations and common, low-effect variants, revealing a continuous genetic spectrum influencing epilepsy risk.
The review also sheds light on the extensive genetic pleiotropy linking epilepsy to psychiatric disorders. Using the MiXeR bivariate model, it was demonstrated that many risk variants that predispose to genetic generalized epilepsy overlap substantially with those for schizophrenia, major depression, bipolar disorder, and anxiety disorders. Interestingly, these overlaps are not always reflected in genome-wide genetic correlations due to a complex pattern of variants influencing phenotypes in opposing directions. Such findings provide a molecular basis for the high rates of psychiatric comorbidity observed clinically in epilepsy patients.
Adding complexity, the authors discuss an intriguing genetic relationship between epilepsy and cortical brain morphology. Approximately 30-40% of common variants contributing to epilepsy risk also influence cortical thickness and surface area, though these traits do not show significant genome-wide genetic correlations. This implies a nuanced interplay of genetic factors, where pleiotropic variants impact multiple phenotypes through intricate and potentially divergent mechanisms.
Clinically, the review adopts a measured stance. While genetic testing has become standard for early-onset syndromic epilepsies, its application in common epilepsy is limited by the complex polygenic nature and scarcity of rare, pathogenic variants in the majority of cases. Polygenic risk scores demonstrate promise in contexts such as risk stratification following a first unprovoked seizure, with hazard ratios comparable to those in cardiovascular genetics. However, given current limitations—including the predominant European ancestry of GWAS cohorts—widespread clinical deployment remains premature and demands greater ancestral diversity to ensure equity.
The review culminates by advocating for larger, more inclusive GWAS to capitalize on epilepsy’s relatively advantageous genetic architecture. Power projections using the MiXeR framework reveal that expanding genetic generalized epilepsy GWAS sample sizes could increase the proportion of heritability explained by genome-wide significant variants from less than 2% to nearly 50%. This yield outpaces many other complex neurological disorders and positions epilepsy genetics research as a highly cost-effective frontier for genomic medicine.
Despite its advances, the field faces critical gaps. Current datasets are geographically and ancestrally narrow, limiting broad applicability. Somatic mosaicism—a potential contributor to focal epilepsy—is scarcely studied. The statistical underpowering of focal epilepsy cohorts hinders robust association detection, and phenotypic precision remains insufficient to capture genetically relevant subtypes. The authors call for coordinated global efforts integrating multi-omic, neuroimaging, clinical, and longitudinal data, enhanced by machine learning, to unravel these complexities and finally translate genetic insights into clinical practice.
This visionary review crafts a pathway from foundational twin studies to sophisticated genomics, revealing an epilepsy genetic architecture rich with shared biological underpinnings, psychiatric overlaps, and actionable research potential. The promise of forthcoming large-scale, diverse, and multimodal studies beckons a new era wherein genetic discoveries will propel precision medicine for epilepsy patients around the world. The authors conclude that while the journey toward clinical translation is ongoing, the genetic signals waiting to be uncovered could revolutionize diagnosis, risk stratification, and treatment in common epilepsies sooner than anticipated.
Subject of Research: People
Article Title: The genetics of common epilepsies
News Publication Date: 10 March 2026
Web References: https://doi.org/10.61373/gp026y.0027
References: Karadag N, Fuhrer J, Heuser K, Andreassen OA, and Smeland OB. The genetics of common epilepsies. Genomic Psychiatry 2026. DOI: https://doi.org/10.61373/gp026y.0027. Epub 2026 Mar 10.
Image Credits: Olav B. Smeland
Keywords: epilepsy genetics, polygenic inheritance, genome-wide association study, genetic generalized epilepsy, focal epilepsy, rare variants, SNP-heritability, psychiatric comorbidity, polygenic risk scores, genetic pleiotropy, mTORC1 pathway, neurogenetics
Tags: complex genetics of common epilepsiesepilepsy and neurological syndromes geneticsgenetic epidemiology of epilepsygenetic risk factors for epilepsy subtypesgenetic variants influencing epilepsy riskgenome-wide association studies in epilepsymolecular genetics advances in epilepsymonogenic versus polygenic epilepsypolygenic architecture of epilepsystatistical modeling in epilepsy geneticstwin studies in epilepsy researchwhole-exome sequencing epilepsy research
