This retrospective cross-sectional study evaluates the effectiveness of the Katia Dolle Method® in reducing the severity of Autism Spectrum Disorder (ASD) in 183 children. The analysis was based on pre- and post-intervention ATEC scores collected between 2017 and 2024. Results show a highly significant reduction in ATEC scores (mean reduction: 39.20 points; p < 0.001), with the most pronounced improvements observed in younger children and those with greater initial severity. Statistical analyses included paired t-tests, ANOVA, and multivariate regression. The most relevant factors influencing outcomes were intervention time, initial severity, and age at onset. The method integrates immunonutrition, regulation of biological systems, and targeted supplementation, based on a naturopathic framework informed by Psychoneuroimmunoendocrinology (PNIE). Although the study lacked a control group and relied on parent-reported ATEC scores, the consistency of the findings across various subscales and participant profiles supports the method’s potential as a complementary approach in ASD care. This open-access publication aims to contribute to the growing scientific discussion on integrative health strategies for neurodevelopmental disorders.