Cortical GABAergic Neuron Dysregulation in Schizophrenia Is Age Dependent.

Background: Cortical GABAergic (gamma-aminobutyric acidergic) neuron dysregulation is implicated in schizophrenia (SCZ), but it remains unclear whether these changes are due to altered cell proportions or per-cell changes in messenger RNA (mRNA) expression. Methods: We analyzed 14 bulk and cell type-specific RNA sequencing (RNA-seq) datasets from 1408 individuals (672 SCZ cases, 736 controls) across 3 neocortical regions. We deconvolved GABAergic cell-subtype proportions from bulk RNA-seq and benchmarked them against single-nucleus RNA-seq and stereological densities from matched donors. We assessed SCZ- and age-associated changes in cell proportions and per-cell gene expression. Results: SCZ was associated with altered proportions of neocortical parvalbumin (PVALB) and somatostatin (SST) cells, depending on the subject's age at death. Younger SCZ cases (age < 70 years) showed reduced PVALB and SST cell proportions, while older cases showed unchanged or increased proportions compared with controls. Earlier-onset SCZ, associated with more severe clinical symptoms, was linked to greater reductions in these cell types. Additionally, there was robust evidence for reduced per-cell SST and vasoactive intestinal peptide mRNA among younger cases with SCZ. Conclusions: These findings suggest that SCZ is associated with complex, age-dependent alterations in GABAergic neurons, particularly affecting PVALB and SST cells. Our study underscores the importance of age-stratified analyses in SCZ, suggesting that distinct pathological processes underlie GABAergic neuron dysregulation across different age and symptom-severity groups and warranting tailored therapeutic approaches.