Ill. Admin. Code tit. 89, § 146.TABLE B
Mental Age Level Equivalents With Level of Functioning
| Adult Mental Age Functional Age | |
| Mild | 8 years, 6 months to 10 years, 1 month |
| Moderate | 6 years, 1 month to 8 years, 5 months |
| Severe | 3 years, 9 months to 6 years, 0 months |
| Profound | Below 3 years, 9 months |
(Source: Added at 47 Ill. Reg. 18051, effective November 21, 2023)