Table 1.
Sample characteristics of 568 twin pairs by zygosity.
| MZ | DZ-same sex | DZ-opposite sex | ||
|---|---|---|---|---|
| Twin Pairs | M (SD) | M (SD) | M (SD) | χ2 / F (p) |
|
|
||||
| K | 128 | 254 | 186 | |
| ASD in one or both twins (%) | 110 (86%) | 210 (83%) | 151 (81%) | 1.23 (.541) |
| Concordant pairs (% of ASD pairs) | 84 (76%) | 71 (34%) | 27 (18%) | 95.54 (<.001) |
| Age of child | 10.6 (4.6) | 9.9 (4.0) | 9.8 (4.0) | 1.42 (.243) |
| Race (% white/Non-Hispanic) | 111 (87%) | 226 (89%) | 164 (88%) | 0.42 (.812) |
| Age of parent | 38.9 (6.4) | 39.3 (6.0) | 39.4 (6.3) | 0.20 (.800) |
| Parent education | 3.5 (1.0) | 3.8 (1.1) | 3.7 (1.0) | 3.55 (.029) |
|
|
||||
| Individual Twins | M (SD) | M (SD) | M (SD) | χ2 / F (p) |
|
|
||||
| N | 256 | 508 | 372 | |
| Individuals with ASD (%) | 194 (76%) | 281 (55%) | 178 (48%) | 50.17 (<.001) |
| Male N (%) | 204 (80%) | 376 (74%) | 186 (50%) | 79.01 (<.001) |
| Completed SCQ (%) | 155 (61%) | 346 (68%) | 257 (69%) | 5.77 (.056) |
| SCQ total – full sample | 18.2 (10.8) | 14.3 (12.0) | 13.5 (13.3) | 6.40 (.002) |
| SCQ total – ASD-affected | 22.0 (8.7) | 20.6 (9.2) | 21.3 (11.6) | 0.58 (.562) |
| SCQ total – non-ASD | 7.9 (9.2) | 6.6 (10.6) | 6.2 (10.4) | 0.35 (.703) |
| Completed SRS (%) | 78 (30%) | 182 (36%) | 149 (40%) | 6.06 (.048) |
| SRS total T – full sample | 71.7 (23.0) | 66.4 (24.1) | 66.9 (23.7) | 1.18 (.308) |
| SRS total T – ASD-affected | 79.2 (19.2) | 77.7 (21.3) | 81.5 (19.9) | 0.64 (.530) |
| SRS total T – non-ASD | 51.9 (20.6) | 53.6 (20.4) | 53.9 (18.7) | 0.72 (.930) |
Note: MZ=monozygotic twin pairs, DZ-same sex=dizygotic same-sex twin pairs, DZ-opposite sex=dizygotic opposite-sex twin pairs. Parent education is coded 1=did not finish high school, 2=high school diploma or equivalent, 3=some college or associate's degree, 4=bachelor's degree, 5=master's degree, 6=doctoral or professional degree. SCQ total = Social Communication Questionnaire total raw score. SRS total = Social Responsiveness Scale total raw score. Concordant pairs is based on the clinical DSM diagnosis.