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. Author manuscript; available in PMC: 2016 May 1.
Published in final edited form as: JAMA Psychiatry. 2015 May;72(5):415–423. doi: 10.1001/jamapsychiatry.2014.3028

Table 2. MZ and DZ Within-Trait and Cross-Trait Twin Correlationsa.

Within-Trait Correlation, r (95% CI)b
 Cross-Twin Correlation, r (95% CI)c
Measure MZ DZ MZ Cross-Trait DZ Cross-Trait
CAST 0.79 (0.77-0.80)d,e 0.31 (0.28-0.33)d,e NA NA
DAWBA 0.82 (0.67-0.90)e 0.22 (0.00-0.42) 0.40 (0.34-0.45)e −0.01 (0.00-0.07)
ADI-R 0.87 (0.77-0.93)e 0.65 (0.55-0.73)e 0.60 (0.54-0.65)e 0.40 (0.35-0.45)e
ADOS 0.77 (0.62- 0.87)e 0.40 (0.26-0.63)e 0.56 (0.49-0.61)e 0.30 (0.23-0.37)e
Best-estimate diagnosis 0.99 (0.98-0.99)e 0.53 (0.41-0.63)e 0.61 (0.57-0.66)e 0.37 (0.31-0.42)e

Abbreviations: See Table 1. CAST, Covariance of the Childhood Autism Spectrum Test; NA, not applicable.

a

Based on 4 bivariate analyses of the CAST score with each diagnostic ASD measure.

b

Maximum likelihood correlations for MZ and DZ twins (including same-sex and opposite-sex DZ pairs) are estimated in a model with the 2 thresholds on the liability to ASD set to population values of broad-spectrum disorder (5%) and ASD (1%) prevalence.

c

For the CAST score, 4 sets of correlations are available because 4 bivariate analyses were performed; here, only 1 is given (the other 3 were of similar value and with overlapping 95% CIs).

d

Maximum likelihood cross-twin, cross-CAST correlation was obtained for each diagnostic variable and the CAST score separately.

e

Indicates significant estimates (ie, 95% CIs not spanning 0).