Table. Correlations between the CARS and IQ score in Twin Pairsa
DZ＼MZ
T1 CARS
T1 CARS
T1 IQ
T2 CARS
-0.266
T1 IQ
-0.582
T2 CARS
-0.211
0.173
0.109
0.220
T2 IQ
a
T2 IQ
0.327
-0.017
-0.016
0.509
-0.260
-0.671
Monozygotic pairs are above each shaded diagonal and, dizygotic pairs are
below each shaded diagonal. T1, twin 1; T2, twin 2.
This table depicts the correlation matrix for the CARS score and the IQ score
in all twins, because we could not stratify twins by sex due to the limited
sample size. Monozygotic correlations are listed above and dizygotic below
each shaded diagonal, respectively. The cross-twin correlations in
monozygotic pairs for the CARS score (0.327) and the IQ score (0.509) were
substantially higher than those observed among dizygotic pairs (–0.211 and
0.220, respectively), suggesting that genetic factor play a causative role in
the CARS score and the IQ score, separately. There was substantial
within-twin negative correlation between the CARS score and the IQ score
(-0.2 to -0.7), corresponding to the often-observed ASD comorbidity with MR.
In contrast, the cross-twin correlations were difficult to interpret, because
the cross-twin correlations between the CARS score and the IQ score in
monozygotic pairs (-0.017 and -0.016) were negative but those observed
among dizygotic pairs (0.109 and 0.173) were positive. These
“raw“ correlations not corrected for ascertainment was difficult to interpret.
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