The Prune-Without-Repair Model for Schizophrenia Cognitive Impairment: Evidence from Convergent GWAS Re-Analyses

Schizophrenia (SCZ) touches roughly one percent of the world's population and exacts a heavy personal and economic toll [1]. The hallucinations and delusions that dominate clinical charts are only half the story; equally disabling are the early-emerging deficits in memory, attention and executive control that shape a patient's chances of finishing school, holding a job, or living independently [2]. Genomic work has confirmed that SCZ is a textbook example of polygenicity. The latest mega-analyses from the Psychiatric Genomics Consortium implicate hundreds of common variants, each exerting a tiny nudge on risk [3]. Turning that long list of loci into a clear biological narrative, however, remains a major hurdle. At present, two developmental processes dominate the conversation. First, growing evidence points to runaway synaptic pruning during adolescence. In a typical brain, complement proteins and microglia trim weak or redundant connections to streamline circuitry; in SCZ, the shears seem over-active, erasing too many synapses [4,5]. Second, a wealth of clinical and pre-clinical data supports the idea that NMDA-type glutamate receptors are under-active, weakening the long-term potentiation needed to stabilise new memories and working-memory traces [6]. How these two pathways intersect—and how that intersection feeds into the cognitive decline so characteristic of SCZ—remains an open question [7]. To probe the link, we revisited the PGC Wave 3 GWAS through three complementary lenses: MAGMA for gene-set enrichment, stratified LD-score regression for partitioning heritability, and transcriptome-wide association studies (TWAS) to infer expression effects. Our focus was genes that govern pruning and plasticity, which we then contrasted with results from a large intelligence GWAS [8; N = 269 867]. Placing the two traits side by side allows us to pinpoint pathways that are unique to SCZ and to generate testable hypotheses about how mis-timed neurodevelopment may erode cognitive function in the disorder.