Patient-derived iPSC organoids were used to investigate early neurodevelopmental alterations, while a separate meta-analysis of peripheral blood gene expression included 293 samples (160 schizophrenia, 133 controls) to explore biomarker potential.<h4>Results</h4>Both <i>GAD1</i> and <i>GAD2</i> were significantly downregulated in postmortem brain samples (meta-analytic effect sizes <-0.5) and in iPSC-derived organoids, supporting the hypothesis that reduced expression of these genes emerges prior to clinical onset and may contribute to disease development. Here, GAD1 is linked to schizophrenia.