title: Sex/gender differences and autism: setting the scene for future research.
abstract: OBJECTIVE
  The relationship between sex/gender differences and autism has attracted a variety of research ranging from clinical and neurobiological to etiological, stimulated by the male bias in autism prevalence. Findings are complex and do not always relate to each other in a straightforward manner. Distinct but interlinked questions on the relationship between sex/gender differences and autism remain underaddressed. To better understand the implications from existing research and to help design future studies, we propose a 4-level conceptual framework to clarify the embedded themes.
  
  
  METHODS
  We searched PubMed for publications before September 2014 using search terms "'sex OR gender OR females' AND autism." A total of 1,906 articles were screened for relevance, along with publications identified via additional literature reviews, resulting in 329 articles that were reviewed.
  
  
  RESULTS
  Level 1, "Nosological and diagnostic challenges," concerns the question, "How should autism be defined and diagnosed in males and females?" Level 2, "Sex/gender-independent and sex/gender-dependent characteristics," addresses the question, "What are the similarities and differences between males and females with autism?" Level 3, "General models of etiology: liability and threshold," asks the question, "How is the liability for developing autism linked to sex/gender?" Level 4, "Specific etiological-developmental mechanisms," focuses on the question, "What etiological-developmental mechanisms of autism are implicated by sex/gender and/or sexual/gender differentiation?"
  
  
  CONCLUSIONS
  Using this conceptual framework, findings can be more clearly summarized, and the implications of the links between findings from different levels can become clearer. Based on this 4-level framework, we suggest future research directions, methodology, and specific topics in sex/gender differences and autism.
authors.affiliation: National Taiwan University Hospital and College of Medicine, Taipei, Taiwan and the Autism Research Centre, University of Cambridge, Cambridge, UK. Electronic address: mcl45@cam.ac.uk.
authors.forename: Meng-Chuan
authors.initials: MC
authors.lastname: Lai
authors.affiliation: University of Cyprus, Nicosia, Cyprus and the Autism Research Centre, University of Cambridge.
authors.forename: Michael V
authors.initials: MV
authors.lastname: Lombardo
authors.affiliation: University of Edinburgh and the Autism Research Centre, University of Cambridge.
authors.forename: Bonnie
authors.initials: B
authors.lastname: Auyeung
authors.affiliation: Centre for Integrative Neuroscience and Neurodynamics, School of Psychology and Clinical Language Sciences, University of Reading, Reading, UK and the Autism Research Centre, University of Cambridge.
authors.forename: Bhismadev
authors.initials: B
authors.lastname: Chakrabarti
authors.affiliation: Cambridge Lifespan Asperger Syndrome Service (CLASS) Clinic, Cambridgeshire and Peterborough National Health Service Foundation Trust, Cambridge, and the Autism Research Centre, University of Cambridge.
authors.forename: Simon
authors.initials: S
authors.lastname: Baron-Cohen
mesh_terms: D001321:Autistic Disorder / Q000145:classification / Q000175:diagnosis / Q000209:etiology; D005260:Female; D006801:Humans; D008297:Male; D012727:Sex Characteristics
keywords: autism; etiology; gender; nosology; sex