title: Digit ratio and autism spectrum disorders in the Avon Longitudinal Study of Parents and Children: a birth cohort study.
abstract: OBJECTIVE
  To investigate whether second-to-fourth digit ratio (2D:4D), a measure commonly used as a proxy for fetal testosterone exposure, is associated with autism spectrum disorders (ASDs), as predicted by the extreme male brain theory of autism.
  
  
  METHODS
  A birth cohort study.
  
  
  METHODS
  The Avon Longitudinal Study of Parents and Children (ALSPAC).
  
  
  METHODS
  6015 ALSPAC children with data on digit ratio, at least 1 outcome measure and information on potential confounding variables (parental occupational class, maternal education and age at digit ratio measurement). Digit ratio was measured by the photocopy and calliper method.
  
  
  RESULTS
  ASD diagnosis (cases were identified previously by record linkage or maternal report) and 4 measures that combine optimally within ALSPAC to predict ASD: the Children's Communication Checklist (coherence subscale), the Social and Communication Disorders Checklist, a repetitive behaviour measure, and the Emotionality, Activity and Sociability scale (sociability subscale). These measures were dichotomised, with approximately 10% defined as the 'risk' group.
  
  
  RESULTS
  Using logistic regression, we examined the association of 2D:4D with ASDs and 4 dichotomised ASD traits. Covariates were occupational class, maternal education and age at 2D:4D measurement. 2D:4D was not associated with ASDs in males (adjusted OR per 1 SD increase in mean 2D:4D, 0.88 (95% CI 0.65 to 1.21), p=0.435) or females (adjusted OR=1.36 (95% CI 0.81 to 2.28), p=0.245). Similar results were observed after adjustment for IQ. There was 1 weak association between reduced coherence and increased left 2D:4D in males, in the opposite direction to that predicted by the extreme male brain theory (adjusted OR=1.15 (95% CI 1.02 to 1.29), p=0.023). Given multiple comparisons, this is consistent with chance.
  
  
  CONCLUSIONS
  In this population-based study, there was no strong evidence of an association between 2D:4D and ASD diagnosis or traits, although the CIs were wide. These results are not consistent with the extreme male brain theory.
authors: Centre for Academic Mental Health, School of Social and Community Medicine, University of Bristol, Bristol, UK MRC Integrative Epidemiology Unit, School of Social & Community Medicine, University of Bristol, Bristol, UK.
authors: Anna Louise
authors: AL
authors: Guyatt
authors: Centre for Academic Mental Health, School of Social and Community Medicine, University of Bristol, Bristol, UK.
authors: Jon
authors: J
authors: Heron
authors: Centre for Academic Mental Health, School of Social and Community Medicine, University of Bristol, Bristol, UK.
authors: Bernice Le Cornu
authors: Ble C
authors: Knight
authors: Centre for Child and Adolescent Health, School of Social & Community Medicine, University of Bristol, Bristol, UK.
authors: Jean
authors: J
authors: Golding
authors: Centre for Academic Mental Health, School of Social and Community Medicine, University of Bristol, Bristol, UK Avon and Wiltshire Partnership NHS Mental Health Trust, Bristol, UK.
authors: Dheeraj
authors: http://orcid.org/0000-0002-7239-3523
authors: D
authors: Rai
mesh_terms: D000067877:Autism Spectrum Disorder / Q000209:etiology / Q000378:metabolism / Q000523:psychology; D001837:Body Weights and Measures; D001921:Brain / Q000378:metabolism*; D002648:Child; D015331:Cohort Studies; D005260:Female; D005385:Fingers; D006801:Humans; D016015:Logistic Models; D008137:Longitudinal Studies; D008297:Male; D010290:Parents; D010641:Phenotype; D013739:Testosterone / Q000378:metabolism*
chemical_list: D013739:Testosterone
keywords: Child & adolescent psychiatry < PSYCHIATRY; Developmental neurology & neurodisability < PAEDIATRICS; EPIDEMIOLOGY