Table 1. Participant characteristics.
| Controls | ADHD | Tests for group differences | ||||||||
| All (n = 83) | ≤12 yr (n = 48) | >12 yr (n = 35) | All (n = 57) | ≤12 yr (n = 26) | >12 yr (n = 31) | All | ≤12 yr | >12 yr | ||
| Gender | N Boys/Girls | 60/23 | 32/16 | 28/7 | 47/10 | 19/7 | 28/3 | .224 | .610 | .314 |
| Age | M (SD) | 12.7 (4.4) | 9.5 (1.4) | 16.9 (3.4) | 12.9 (4.0) | 9.6 (1.6) | 15.7 (3.2) | .745 | .958 | .132 |
| Range | 7.0–27.9 | 7.0–11.8 | 12.0–27.9 | 6.6–23.5 | 6.6–11.9 | 12.0–23.5 | ||||
| Total IQ | M (SD) | 111.9 (17.5) | 113.7 (18.2) | 109.4 (16.3) | 101.4(17.4) | 105.9 (19.6) | 97.7 (14.5) | .001 | .093 | .003 |
| Range | 76–152 | 78–152 | 76–143 | 72–144 | 72–144 | 73–125 | ||||
| DISC-IV/MINI-Plus | ADHD Inattentive | 17 | 6 | 11 | ||||||
| ADHD Hyperactive/Impulsive | 4 | 2 | 2 | |||||||
| ADHD Combined | 36 | 18 | 18 | |||||||
| ODD (DISC only) | 18 | 10 | 8 | |||||||
| CBCL/ASRa | Internalising raw score M (SD)d | 4.3 (4.9) | 4.5 (5.4) | 3.9 (3.8) | 7.7 (5.5) | 8.0 (6.2) | 7.5 (4.9) | <.001 | .021 | .005 |
| Externalising raw score M (SD)d | 3.6 (3.8) | 4.0 (4.2) | 2.9 (3.0) | 12.7 (8.6) | 13.9 (8.8) | 11.4 (8.5) | <.001 | <.001 | <.001 | |
| SESb | Education father (years) | 13.6 (2.3) | 13.4 (2.4) | 14.0 (2.2) | 12.5 (3.0) | 12.5 (3.5) | 12.6 (2.6) | .028 | .275 | .028 |
| Education mother (years) | 13.3 (2.4) | 13.3 (2.4) | 13.4 (2.3) | 12.7 (2.7) | 12.7 (3.3) | 12.7 (2.3) | .159 | .405 | .239 | |
ADHD, Attention-Deficit/Hyperactivity Disorder; ASR, Adult Self Report; ODD, Oppositional Defiant Disorder; DISC-IV, Diagnostic Interview Schedule for Children-Fourth Edition; CBCL, Child Behavior Checklist; MINI-Plus, Mini International Neuropsychiatric Interview Plus; SES, Socio-Economic Status.
Reported are: t-tests for continuous variables, Fisher Exact test for gender (due to low cell counts and large cell count differences) and Chi2 for subtypes by age group (as Fisher Exact tests cannot be applied to 3×2 tables).
a. Unavailable for 11 controls and 8 subjects with ADHD.
b. Data father unavailable in 3 controls and 7 subjects with ADHD, data mother unavailable in 1 control and 7 subjects with ADHD.