Table 3.
Estimated Fraction of Variation Explained for Liability of ASD, AD, and SD, and Estimated Coefficient for Fixed Parameters
| Estimatesa (95% CI) | Outcome | ||
|---|---|---|---|
| ASD | AD | SD | |
| Estimated Variance for Random Components (Fractions of Variation Explained) | |||
| Maternal effect | 0.004 (0, 0.052) | 0.001 (0, 0.074) | 0.007 (0.002, 0.068) |
| Additive genetic effect | 0.848 (0.731, 0.873) | 0.796 (0.612, 0.851) | 0.764 (0.630, 0.825) |
| Shared environmental effect | 0.002 (0, 0.037) | 0.007 (0, 0.097) | 0.002 (0, 0.047) |
| Unshared environmental effect | 0.147 (0.120, 0.201) | 0.195 (0.135, 0.274) | 0.227 (0.163, 0.293) |
| Estimated Coefficient for Fixed Parametersb | |||
| Gender, male | 0.395 (0.385, 0.401) | 0.372 (0.362, 0.387) | 0.356 (0.347, 0.367) |
| Birth cohort, 2003–2007 | −0.246 (−0.259, −0.237) | −0.093 (−0.104, − 0.077) | −0.324 (−0.338, − 0.309) |
AD, autistic disorder; ASD, autism spectrum disorder; CI, confidence interval; SD, Asperger and pervasive development disorders not otherwise specified combined.
The mixed model used a probit link. Random effects used in the liability model included maternal effect, direct genetic effect, shared environmental effect, and unshared environmental effect, and sex (1 = male, 0 = female) and birth cohort (1 = 2003–2007 cohort, 0 = 1998–2002 cohort) as fixed parameters. Coefficient for fixed effects indicates outcome risk associated with certain variable, while adjusted for other parameters.
The reported probit-link values for fixed parameters are in standard normal quantile scale.