Mental disorder / illness is not the same as an intellectual disability
There is a difference between a mental disorder / illness and an intellectual disability. Intellectual disability is the new term for mental retardation.
The term mental disorder / illness refers to someone who has a condition like Schizophrenia or Bipolar Disorder. These conditions are not intellectual disabilities. Someone who has an intellectual disability may or may not also have a mental disorder / illness. Also, someone who has a mental illness might not have an intellectual disorder. In fact, there have been some geniuses who have had schizophrenia.