CHI3L1 and Alzheimer disease: Among them, Nrf2 is a core target that co‐occurs in all three diseases (MS, AD, and psychiatric disorders), while molecules such as IL‐3 (MS, AD), TGF‐β1 (MS, ALS), C1q (AD, ALS), CHI3L1 (MS, AD), and NMDAR (psychiatric disorders, HD) play a role in both diseases.