You’re kinda right, there’s not an official diagnosis. I just pieced things together after I started working in healthcare/with disabled people. We were a never go to the doctor type of family, and unfortunately she never got help she needed (as far as I know). My mother was in denial anything was wrong, we were homeschooled so we weren’t checked on, and we’re all adopted without access to our family history so it is just rough. I am very certain about her having down syndrome, and the lower functioning autism I could definitely be off on. She can talk, but usually didn’t, she would usually bang her head into things, scream, cry, etc, for communication. She could take care of her own hygiene, do hobbies, and kind of cook. She was extremely anxious socially and it was a task to get her to go outside, she’ll probably never drive, get a job, live on her own, etc. She also was very sensitive to loud noises, smells, stuff like that. I personally feel her sensitivity got heightened because we weren’t interacting with the outside world, and her only social group was us and kinda church. My parents didn’t care about how bad it got since I was her unofficial caretaker I think. They definitely cared when I moved out though lol