title: A longitudinal twin study of the association between childhood autistic traits and psychotic experiences in adolescence.
abstract: BACKGROUND
  This twin study investigated whether autistic traits during childhood were associated with adolescent psychotic experiences.
  
  
  METHODS
  Data were collected from a community sample of approximately 5000 twin pairs, which included 32 individuals with diagnosed autism spectrum conditions (ASC). Parents rated autistic traits in the twins at four points between ages 8-16 years. Positive, negative, and cognitive psychotic experiences were assessed at age 16 years using self- and parent-report scales. Longitudinal twin analyses tested the associations between these measures.
  
  
  RESULTS
  Autistic traits correlated weakly or nonsignificantly with positive psychotic experiences (paranoia, hallucinations, and grandiosity), and modestly with cognitive psychotic experiences (cognitive disorganisation). Higher correlations were observed for parent-rated negative symptoms and self-reported anhedonia, although the proportion of variance in both accounted for by autistic traits was low (10 and 31 %, respectively). The majority of the genetic influences on negative symptoms and anhedonia were independent of autistic traits. Additionally, individuals with ASC displayed significantly more negative symptoms, anhedonia, and cognitive disorganisation than controls.
  
  
  CONCLUSIONS
  Autistic traits do not appear to be strongly associated with psychotic experiences in adolescence; associations were also largely restricted to negative symptoms. Of note, the degree to which the genetic and environmental causes of autistic traits influenced psychotic experiences was limited. These findings thus support a phenotypic and etiological distinction between autistic traits and psychotic experiences.
authors.affiliation: Centre for Brain and Cognitive Development, Department of Psychological Sciences, Birkbeck, University of London, London, UK.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Taylor
authors.affiliation: Analytic and Translational Genetics Unit, Department of Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, MA USA ; Stanley Center for Psychiatric Research and Program in Medical and Population Genetics, Broad Institute of Harvard and MIT, Cambridge, MA USA.
authors.forename: Elise B
authors.initials: EB
authors.lastname: Robinson
authors.affiliation: MRC Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, Psychology & Neuroscience, King's College, London, UK.
authors.forename: Francesca
authors.initials: F
authors.lastname: Happé
authors.affiliation: Department of Child Psychiatry and MRC SGDP Centre, Institute of Psychiatry, Psychology & Neuroscience, King's College, London, UK.
authors.forename: Patrick
authors.initials: P
authors.lastname: Bolton
authors.affiliation: Department of Psychiatry, University of Oxford, Oxford, UK.
authors.forename: Daniel
authors.initials: D
authors.lastname: Freeman
authors.affiliation: Centre for Brain and Cognitive Development, Department of Psychological Sciences, Birkbeck, University of London, London, UK.
authors.forename: Angelica
authors.initials: A
authors.lastname: Ronald
keywords: Autism; Comorbidity; Genetics; Psychotic experiences; Twin study