Elsevier

Biological Psychiatry

Volume 57, Issue 6, 15 March 2005, Pages 655-660
Biological Psychiatry

Original articles
Intergenerational transmission of subthreshold autistic traits in the general population

https://doi.org/10.1016/j.biopsych.2004.12.014Get rights and content

Background

Autistic disorder (AD) is a disabling oligogenic condition characterized by severe social impairment. Subthreshold autistic social impairments are known to aggregate in the family members of autistic probands; therefore, we conducted this study to examine the intergenerational transmission of such traits in the general population.

Methods

The Social Responsiveness Scale (SRS), a quantitative measure of autistic traits, was completed on 285 pairs of twins (by maternal report) and on their parents (by spouse report).

Results

Correlation for social impairment or competence between parents and their children and between spouses was on the order of .4. In families in which both parents scored in the upper quartile for social impairment on the SRS, mean SRS score of offspring was significantly elevated (effect size 1.5). Estimated assortative mating explained approximately 30% of the variation in parent SRS scores.

Conclusions

Children from families in which both parents manifest subthreshold autistic traits exhibit a substantial shift in the distribution of their scores for impairment in reciprocal social behavior, toward the pathological end. As has been previously demonstrated in children, heritable subthreshold autistic impairments are measurable in adults and appear continuously distributed in the general population.

Section snippets

Methods and materials

For the biological parents of 285 epidemiologically ascertained twin pairs (subjects of the ongoing Missouri Twin Study; Constantino and Todd 2003), we obtained spouse-report parent assessments (mother reporting about father and father reporting about mother) and maternal-report assessments of twins using the Social Responsiveness Scale (SRS), a quantitative measure of autistic traits (Constantino et al 2000). All of the families had been participants in a previous study (Constantino and Todd

Results

SRS scores were unrelated to parental age and were continuously distributed in both mothers and fathers (Figure 1). Intraclass correlations for pairings of family members were highly statistically significant (in all cases p < .00001): mother-daughter .41, mother-son .38, father-daughter .49, father-son .58. Intraclass correlation between mothers and fathers was .38, suggestive (at the simplest level of analysis) of the presence of assortative mating.

Figure 2 depicts variation in offspring SRS

Discussion

Data from this intergenerational study of autistic traits confirmed previous findings of substantial genetic influence on subthreshold autistic traits (Constantino and Todd 2003) and extends our heritability estimates to adults. The condition of having both parents within the top quartile of their respective distributions for degree of autistic social impairment resulted in a substantial pathologic shift in the distribution of scores for autistic social impairment in offspring, with an effect

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