Table 2.
Summary of characteristics of ADHD subjects, by level of IQ.
| Characteristic | High IQ (IQ ≥ 120; N=34) | Normal IQ (80≤IQ<120; N=276) | Low IQ (IQ<80; N=21) | P-value |
|---|---|---|---|---|
| Male gender, n (%) | 31 (91.2) | 202 (73.2) | 14 (66.7) | 0.052 |
| Maternal education at birth, n (%) | <0.001 | |||
| Less than high school | 0 | 27 (9.8) | 0 | |
| High school graduate | 8 (23.5) | 101 (36.6) | 11 (52.4) | |
| Some post secondary | 9 (26.5) | 91 (33) | 5 (23.8) | |
| College graduate | 15 (44.1) | 32 (11.6) | 3 (14.3) | |
| Unknown | 2 (5.9) | 25 (9.1) | 2 (9.5) | |
| Age met AD/HD research criteria (years) | 0.64 | |||
| Mean (SD) | 10.5 (3.4) | 10.3 (3.5) | 11.1 (3.4) | |
| Median | 9.5 | 9.7 | 9.8 | |
| Range | (4.5–17.8) | (2.3–22.1) | (6.6–17.3) | |
| LD by MN, DIS, or LA research criteria, n (%) | 29 (85.3) | 216 (78.3) | 16 (76.2) | 0.61 |
| Psychiatric disorder prior to 18 years of age, n (%) | 16 (47.1) | 139 (50.4) | 10 (47.6) | 0.92 |
| Substance abuse prior to 18 years of age, n (%) | 6 (17.6) | 65 (23.6) | 4 (19.0) | 0.68 |
LD, Learning Disability; MN, State of Minnesota regression-based discrepancy formula for determining the presence of LD; DIS, non regression-based discrepancy formula for determining presence of LD; LA, Low Achievement, non discrepancy-based formula for determining presence of LD.