Update (September 2025): This preprint has now been peer-reviewed and formally published in the MSI Journal of Multidisciplinary Research (MSIJMR). You can access the published version here: https://doi.org/10.5281/zenodo.17007271 Abstract Autism spectrum disorders (ASD) may arise from a convergence of dietary, immunological, and developmental factors. We propose the “autism cascade hypothesis,” a novel mechanistic framework in which digestion of A1 B-casein releases B-casomorphin-7 (BCM-7), compromising blood-brain barrier (BBB) integrity and enabling peripheral immune cell infiltration. This cascade culminates in astrocyte injury and neuroimmune activation, potentially amplified by routine infant vaccination during periods of BBB vulnerability. Drawing from biochemical, neuroimmunological, and developmental literature, we outline a testable model that integrates molecular checkpoints and environmental timing. This hypothesis offers a foundation for future research, risk-stratified interventions, and community education. Keywords: Autism spectrum disorder; B-casomorphin-7; blood-brain barrier; neuroinflammation; vaccination; A1 B-casein.