Table 1.
Participant characteristics of the twins (N = 1,347) and clinical cases (N = 183).
| Twins | Clinical cases | ||||
|---|---|---|---|---|---|
| Concordant low | Discordant | Concordant high | |||
| n = 605 | Low (n = 189) | High (n = 189) | n = 364 | n = 183 | |
| N complete twin pairs | 302 | 189 | 182 | - | |
| Mean (SD) age sample collection | 9.4 (1.9) | 10.1 (1.7) | 9.5 (1.8) | 10.2 (1.8) | |
| Range age sample collection | 5.6–12.6 | 6.1–12.7 | 5.8–12.9 | 6.3–13.4 | |
| N (%) MZ twins | 469 (77.5%) | 306 (81.0%) | 330 (90.7%) | ||
| N (%) females | 323 (53.4%) | 85 (45.0%) | 79 (41.8%) | 159 (43.7%) | 47 (25.7%) |
| CBCL mother (SD) aggression score | 2.7 (3.8) | 4.4 (4.4) | 6.2 (5.8) | 7.6 (6.0) | 13.0 (7.6) |
| Current psychotropic medication use | |||||
| Stimulants | 10 (1.7%) | 7 (3.7%) | 13 (6.9%) | 25 (7.0%) | 46 (24.6%) |
| Analgesics | 1 (0.2%) | 1 (0.5%) | 3 (1.6%) | 1 (0.3%) | 0 (0.0%) |
| Antipsychotics | 1 (0.2%) | 0 (0.0%) | 1 (0.5%) | 3 (0.8%) | 36 (19.7%) |
| Hypnotics/sedatives | 7 (1.2%) | 1 (0.5%) | 2 (1.1%) | 6 (1.7%) | 6 (3.3%) |
CBCL, Child Behavior Checklist; MZ, monozygotic. The clinical cases CBCL scores include either mother of father-report (90% mother report).