405 ILCS 5/1-129

(405 ILCS 5/1-129) Sec. 1-129. Mental illness. "Mental illness" means a mental, or emotional disorder that substantially impairs a person's thought, perception of reality, emotional process, judgment, behavior, or ability to cope with the ordinary demands of life, but does not include a developmental disability, dementia or Alzheimer's disease absent psychosis, a substance use disorder, or an abnormality manifested only by repeated criminal or otherwise antisocial conduct. (Source: P.A. 100-759, eff. 1-1-19.)