In this study we examined the genetic structure of reciprocal social behavior (RSB) - a core component of the autistic phenotype - as a function of gender. Methods: The sample consisted of 232 pairs of male twins, 324 pairs of female twins, and 126 opposite sex twin pairs, all subjects age 7-15 years. One parent of each pair of twins completed the Social Reciprocity Scale (SRS) on their children. The data were subjected to structural equation modeling using the statistical software, Mx. Results: Scale scores for RSB in males were stongly influenced by additive genetic factors (accounting for approximately 76 percent of the total trait variance), exhibited minimal measurement error, and were not significantly influenced by age, rater bias or rater contrast effects. For females, the magnitude of additive genetic influences on RSB was 0.33. For opposite sex pairs, the best fitting model was one which incorporated gender-specific genetic influences, the magnitude of which was 0.26. Conclusion: Given these findings, and given the fact that autism spectrum disorders are more commonly observed in boys than in girls, it appears possible that susceptibility loci accounting for a substantial share of the variance in subthreshold autistic traits may reside on the X chromosome.
|Number of pages||2|
|Journal||American Journal of Medical Genetics - Neuropsychiatric Genetics|
|State||Published - Oct 8 2001|