You end up with symptoms of a lot of different mental disorders that have a different underlying cause than normal for those disorders.
For example, I have a rather severe impairment of executive function. I have a diagnosis of ADHD, but my internal experience doesn’t seem to match what I’ve read about other people with ADHD and none of the first or second line treatments for ADHD work on me.
I also have a significant overlap in the symptoms of autism, but I do not have the internal experience of someone who is autistic.