This dataset supports the article titled "Comparative analysis of fecal microbiota between adolescents with early-onset psychosis and adults with schizophrenia.", available at https://doi.org/10.3390/microorganisms12102071. The dataset includes fecal microbiota sequencing data from adolescent patients with early-onset psychosis, adult patients with schizophrenia, and non-psychotic controls. The data were generated using 16S rRNA gene sequencing and analyzed with QIIME2 and PICRUSt2 to assess microbial diversity and functional pathways. Variables such as age, diagnosis, and medication use are included. The dataset contains: Processed results from fecal microbiota analysis (OTUs and taxonomic classifications) Metadata associated with each sample (age, diagnosis, medication) Results from diversity analysis (alpha and beta diversity metrics) Functional analysis of microbial pathways (PICRUSt2) These data are essential for reproducing the findings discussed in the article. Note that the raw sequencing data are available upon request.