Autism is not a mental illness. And yes, it shows early in life. Sometimes it is missed depending on how forgiving the surroundings are for unusual behavior. I was never seen as odd as a child even if I have AS/ADD.

There is no treatment that makes autism go away. You can get training where you work with your weak points, some have a hard time with things like abstraction and spacial awareness, different problems for different auties. And language training for those who need it. On a higher level you can get help practicing social and practical skills. Many people think with autism you only have issues with social skills, but oftentimes there are issues with self care spanning from mild to severe. Myself I completely suck at organizing and picking up after myself....

Autism does not happen because of how you were raised.