Evidence That Autistic Traits Show the Same Etiology in the General Population and at the Quantitative Extremes (5%, 2.5%, and 1%)

Abstract

Context Genetic factors play an important role in the etiology of both autism spectrum disorders (ASD) and autistic traits. However, little is known about the etiologic consistency of autistic traits across levels of severity. Objective We compared the etiology of typical variation in autistic traits with extreme scoring groups (including top 1%) which mimicked the prevalence of diagnosed ASD in the largest twin study of autistic traits to date. Design Twin study employing phenotypic analysis and genetic model-fitting in the total sample and extreme scoring groups (top 5%, 2.5%, 1%). Setting A nationally-representative general population twin sample from the United Kingdom. Participants The families of 5,988 12-year-old pairs in the Twin Early Development Study. Main Outcome Measure Autistic traits as assessed by the Childhood Autism Spectrum Test. Results Moderate to high heritability was found for autistic traits in the general population (52% for females; 76% for males). High heritability was found in extreme scoring groups. There were no differences in heritability among extreme groups or between the extreme groups and the general population. A continuous liability shift towards autistic trait affectedness was seen in the cotwins of individuals scoring in the top 1%, suggesting shared etiology between extreme scores and normal variation. Conclusions This evidence of similar etiology across normal variation and the extremes has implications for molecular genetic models of ASD and for conceptualizing ASD as the quantitative extreme of a neurodevelopmental continuum.

Understanding sex bias in autism spectrum disorder

“…This approach is based on the assumption that the distribution of etiological contributors to ASD is not modal, with different etiologies driving mild presentations and the most severe manifestations of autistic traits, but is instead continuous, with the same etiological contributors driving subthreshold and severe presentations of autistic behavior. Observations of subthreshold autistic-like traits, often referred to as the broader autism phenotype, in family members of autistic cases are consistent with this model (16), and previous work from Robinson et al (17) in the Twins Early Development Study cohort has demonstrated a continuous shift toward higher autistic behavior scores in cotwins of probands across a range of severity, from those scoring above the 90th, 95th, and 99th percentiles.…”

An Oxytocin-Induced Facilitation of Neural and Emotional Responses to Social Touch Correlates Inversely with Autism Traits

“…ASDs have been reported to represent the extreme end of a normal distribution of autistic-like traits, suggesting that these disorders, and autistic-like traits, are etiologically linked (Robinson et al, 2011;Lundstrom et al, 2012). In the present study, we tested healthy men with a mean AQ score of 13.20 ± 4.64, whereas ASD patient samples typically display peak scores of 35.8±6.5 ( Baron-Cohen et al, 2001).…”

Associations between oxytocin-related genes and autistic-like traits

“…The importance of genetic factors in the etiology of ASD has repeatedly been demonstrated in twin studies, with heritability estimates of 70-90% (Bailey et al, 1995;Lichtenstein et al, 2010;Rosenberg et al, 2009). Moreover, ALTs and ASD have been shown to share common genetic influences (Lundstrom et al, 2012;Robinson et al, 2011). The theoretical division into the three symptom dimensions mentioned above has been confirmed in several studies (Happe and Ronald, 2008), and these domains have been indicated to have partly separate genetic influences when investigated in the general population .…”