Table 2.
ACE model parameter estimates in concordant ASD and TD twin pairs
| A (additive genetics) | C (shared environment) | E (unique environment) | ||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| ASD | CI | P | TD | CI | P | ASD | CI | P | TD | CI | P | ASD | CI | TD | CI | |
| Frontal lobe | ||||||||||||||||
| Total volume | 0.94 | [0.70, 1.18] | <0.001† | 0.77 | [0.55, 1.00] | <0.001† | x | x | x | x | x | x | 0.06 | [−0.18, 0.30] | 0.23 | [0.003, 0.45] |
| GM volume | x | x | x | - | - | - | 0.79 | [0.63, 0.95] | <0.001† | x | x | x | 0.21 | [0.05, 0.37] | - | - |
| WM volume | 0.86 | [0.58, 1.14] | <0.001† | 0.84 | [0.63, 1.05] | <0.001† | x | x | x | x | x | x | 0.14 | [−0.14, 0.42] | 0.16 | [−0.05, 0.37] |
| Thickness | x | x | x | 0.60 | [0.37, 0.83] | <0.001† | 0.81 | [0.71, 0.92] | <0.001† | x | x | x | 0.19 | [0.08, 0.29] | 0.40 | [0.17, 0.63] |
| Surface area | 1.00 | [0.78, 1.21] | <0.001† | 0.73 | [0.43, 1.03] | <0.001† | x | x | x | x | x | x | 0.01 | [−0.21, 0.22] | 0.27 | [−0.03, 0.57] |
| Temporal lobe | ||||||||||||||||
| Total volume | 0.81 | [0.46, 1.15] | <0.001† | 0.80 | [0.48, 1.12] | <0.001† | x | x | x | x | x | x | 0.19 | [−0.15, 0.54] | 0.20 | [−0.12, 0.52] |
| GM volume | 0.86 | [0.60, 1.12] | <0.001† | 0.74 | [0.41, 1.07] | <0.001† | x | x | x | x | x | x | 0.14 | [−0.12, 0.40] | 0.26 | [−0.07, 0.59] |
| WM volume | 0.80 | [0.44, 1.15] | <0.001† | 0.89 | [0.64, 1.13] | <0.001† | x | x | x | x | x | 0.21 | [−0.15, 0.56] | 0.11 | [−0.13, 0.36] | |
| Thickness | x | x | x | 0.33 | [0.04, 0.63] | 0.03† | 0.77 | [0.60, 0.93] | <0.001† | x | x | x | 0.24 | [0.07, 0.40] | 0.67 | [0.37, 0.96] |
| Surface area | 0.87 | [0.64, 1.11] | <0.001† | 0.79 | [0.50, 1.08] | <0.001† | x | x | x | x | x | x | 0.13 | [−0.11, 0.36] | 0.21 | [−0.08, 0.50] |
| Parietal lobe | ||||||||||||||||
| Total volume | 0.85 | [0.44, 1.25] | <0.001† | 0.75 | [0.50, 0.99] | <0.001† | x | x | x | x | x | x | 0.16 | [−0.25, 0.56] | 0.25 | [0.09, 0.50] |
| GM volume | 1.00 | [0.77, 1.25] | <0.001† | 0.76 | [0.54, 0.98] | <0.001† | x | x | x | x | x | x | 0.00 | [−0.25, 0.23] | 0.24 | [0.02, 0.46] |
| WM volume | 0.80 | [0.40, 1.19] | <0.001† | 0.88 | [0.59, 1.07] | <0.001† | x | x | x | x | x | x | 0.20 | [−0.19, 0.60] | 0.12 | [−0.07, 0.41] |
| Thickness | x | x | x | 0.63 | [0.43, 0.83] | <0.001† | 0.87 | [0.77, 0.97] | <0.001† | x | x | x | 0.13 | [0.03, 0.24] | 0.37 | [0.17, 0.57] |
| Surface area | 0.89 | [0.68, 1.10] | <0.001† | - | - | - | x | x | x | x | x | x | 0.11 | [−0.10, 0.32] | - | - |
| Occipital lobe | ||||||||||||||||
| Total volume | 0.76 | [0.45, 1.06] | <0.001† | 0.80 | [0.62, 0.97] | <0.001† | x | x | x | x | x | x | 0.24 | [−0.06, 0.55] | 0.21 | [0.03, 0.38] |
| GM volume | 0.93 | [0.70, 1.16] | <0.001† | 0.80 | [0.60, 1.00] | <0.001† | x | x | x | x | x | x | 0.07 | [−0.16, 0.30] | 0.20 | [0.00, 0.40] |
| WM volume | 0.70 | [0.34, 1.07] | <0.001† | 0.89 | [0.74, 1.05] | <0.001† | x | x | x | x | x | x | 0.30 | [−0.07, 0.67] | 0.11 | [−0.05, 0.26] |
| Thickness | 0.93 | [0.75, 1.11] | <0.001† | x | x | x | x | x | x | 0.61 | [0.45, 0.77] | <0.001† | 0.07 | [−0.11, 0.25] | 0.39 | [0.23, 0.55] |
| Surface area | 0.81 | [0.53, 1.10] | <0.001† | 0.69 | [0.45, 0.94] | <0.001† | x | x | x | x | x | x | 0.19 | [−0.10, 0.47] | 0.31 | [0.06, 0.56] |
The ACE model for broad sense heritability was calculated separately for twin pairs in which both twins were diagnosed with ASD or were TD controls based on Falconer’s formula (Falconer 1981) [a = additive genetics; c = shared family environment; e = unique environment] utilizing a bootstrapping method to calculate estimates across 1000 repetitions. Twin pairs discordant for ASD were excluded. When A or C was nonsignificant within the model (x), a constrained AE or CE model was utilized. When model assumptions were violated, model estimates were not generated, but the model parameters that would have been most appropriate based on ICC estimates are indicated (−). E estimates were based on the residuals and were not tested for significance. Significant model parameter at *P < 0.05 and †false discovery rate (Benjamini and Hochberg 1995) correction across the estimates within each column are indicated.