This study will investigate why IGF-1 receptor (IGF-1R)–related medicines, approved for the treatment of Rett syndrome, produce their therapeutic effects and adverse events.Specifically, we will focus on the mTORC1 pathway, which operates downstream of IGF-1R signaling, and on mitochondria—the cell’s “power plants”—to clarify at the molecular level how these mechanisms contribute to a drug’s benefits and side effects.Ultimately, in line with the wishes of people with lived experience and their families, we aim to facilitate the development of more effective and safer treatments for autism spectrum disorder and schizophrenia, and to establish biomarkers that help identify individuals who are most likely to benefit.