[A twin study on intelligence and processing speed heritability of children and adolescent].
OBJECTIVE
To explore the effects of the genetic and environmental factors on intelligence of children and adolescent from the Southwest China Prospective Twin Registry (SCPT).


METHODS
The intelligence was investigated by using the Wechsler Intelligence Scale for Children (C-WISC) in 333 twin pairs aged 6-16 years. The effects of genetic and environmental factors on IQ were analyzed by using structural equation modeling (SEM) and correlation analysis method. The effects in different sex and age groups in this population were also investigated.


RESULTS
Genetic influence accounted for 0.43 of total IQ variance and 0.37 of verbal IQ in 6-16 years old children and adolescent, but there was no significant genetic effect on performance IQ. The heritability of children aged 10-16 years was higher than that of those aged 6-10 years (total IQ: 0.82 vs 0.00, verbal IQ: 0.80 vs 0.00, performance IQ:0.51 vs 0.00). In males the heritability of verbal IQ (0.47) was higher than that in females (0.05). The shared environmental influences accounted fo r the majority of variance of performance IQ in both males and females.


CONCLUSIONS
There is moderate heritability on the total IQ and verbal IQ, while shared environmental factors played important roles on the variance of performance IQ. The heritability of IQ, verbal IQ and performance IQ are higher in older children and adolescent than that in younger children.
Zhang
Xiao-wei
XW
Mental Health Center, West China Hospital, Sichuan University, Chengdu, Sichuan, 610041 PR China.
Huang
Yi
Y
Xiang
Yun
Y
Gao
Xin
X
Situ
Ming-jing
MJ
Fang
Hui
H
Zhang
Yi
Y
Fu
Yi-xiao
YX
Jia
Lu
L
Meng
Hua-qing
HQ
Ma
Xiao-hong
XH
Wang
Ying-cheng
YC
Liu
Xie-he
XH
Li
Tao
T
D000293:Adolescent; D000367:Age Factors; D002648:Child; D002657:Child Development / Q000502:physiology; D004777:Environment; D005260:Female; D006801:Humans; D007360:Intelligence / Q000235:genetics*; D008297:Male; D011597:Psychomotor Performance / Q000502:physiology*; D011930:Reaction Time / Q000235:genetics*; D012727:Sex Characteristics; D012737:Sex Factors; D014427:Twins / Q000235:genetics*; D014888:Wechsler Scales