RT Journal
A1 Robinson EB, Koenen KC, McCormick MC, et al
T1 EVidence that autistic traits show the same etiology in the general population and at the quantitative extremes (5%, 2.5%, and 1%)
JF Archives of General Psychiatry
JO Archives of General Psychiatry
YR 2011
FD November 1
VO 68
IS 11
SP 1113
OP 1121
DO 10.1001/archgenpsychiatry.2011.119
UL http://dx.doi.org/10.1001/archgenpsychiatry.2011.119
AB Context 
                  Genetic factors play an important role in the etiology of both autism spectrum disorders and autistic traits. However, little is known about the etiologic consistency of autistic traits across levels of severity.Objective 
                  To compare the etiology of typical variation in autistic traits with extreme scoring groups (including top 1%) that mimicked the prevalence of diagnosed autism spectrum disorders in the largest twin study of autistic traits to date.Design 
                  Twin study using phenotypic analysis and genetic model-fitting in the total sample and extreme scoring groups (top 5%, 2.5%, and 1%).Setting 
                  A nationally representative twin sample from the general population of England.Participants 
                  The families of 5968 pairs aged 12 years old in the Twins’ 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 (53% for females and 72% 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 toward autistic trait affectedness was seen in the cotwins of individuals scoring in the top 1%, suggesting shared etiology between extreme scores and normal variation.Conclusion 
                  This evidence of similar etiology across normal variation and the extremes has implications for molecular genetic models of autism spectrum disorders and for conceptualizing autism spectrum disorders as the quantitative extreme of a neurodevelopmental continuum.