Men and boys are more frequently diagnosed with autism than women and girls. It is debated whether this is due to a sex difference in rates of autism spectrum disorders (ASD) or whether females are underdiagnosed.[1][2] The prevalence ratio is often cited as about 4 males for every 1 female diagnosed.[3] Other research indicates that it is closer to 3:1 or 2:1.[2][4] One in every 42 males and one in 189 females in the United States is diagnosed with autism spectrum disorder.[5] There is some evidence that females may also receive diagnoses somewhat later than males; however, thus far results have been contradictory.[6]
Several theories exist to explain the sex-based discrepancy, such as a genetic protective effect,[7][8][9] the extreme male brain theory[10][11][12] and phenotypic differences in the presentation between sexes,[9][13][14][15] which may all be intertwined. Researchers have also debated whether a diagnostic gender bias has played a role in females being underdiagnosed with autism spectrum disorder.[16] Researchers have also speculated a gender bias in parental reporting due to the expectations and socialization of gender roles in society.[17]
Since autism is a largely genetic and hereditary condition, genetic factors that lead to differences depending on sex come into play, such as the role of androgen signaling in male development or X-linked mutations, whose associated genetic conditions are typically more common and severe in males. The extreme male brain theory suggests that autistic brains show an exaggeration of the features associated with male brains, such as increased size and decreased relative connectivity as well as systematic thinking over empathetic thinking.[18] The imprinted brain hypothesis suggests genomic imprinting is at least partly responsible for the sex differences in autism and points to the evidence for a common genetic cause with schizophrenia.[19][20][21]
Compared to men, women are generally required to be more impaired by their autism[22] or have more cognitive or behavioral conditions[23] than their male counterparts to meet autism spectrum criteria. There is evidence of increased incidence of social anxiety,[14]anorexia nervosa[24][25] and self-harm in autistic females,[26] though the increased rates of anorexia nervosa and other eating disorders[27] may be due to confusion or conflation with avoidant/restrictive food intake disorder (ARFID), which is particularly common in autism.[28]
Some studies have found that autistic girls and women show higher social motivation and a greater capacity for typical friendships than autistic boys and men.[29][30] Other studies have found that females are more likely to avoid social contact, while males are more likely to attempt social contact while remaining unaware of their social deficits.[31] Similar to the "female phenotype" of ADHD, research has shown that women with autism are less likely to be hyperactive, impulsive, have issues with conduct or stereotyped behavioral traits,[32][33] and have been shown to mask their autistic behaviors and social difficulties more frequently than autistic men.[34] Autistic males often exhibit more easily observed behaviors at a younger age resulting in parental observance and subsequent evaluation of the child. In contrast, behavior of young females is more often overlooked, regardless of any associated at-risk factors[broken anchor] for ASD or other developmental delays. Ultimately, this may contribute to females more frequently receiving their ASD diagnosis later in life than their male counterpart.[35] There is a growing consensus among neuroscientists that the number of autistic women has been vastly underrepresented due to the assumption that it is primarily a male condition.[36]
^ abLudlow, Amanda K.; Roberts, Hannah; Gutierrez, Roberto (1 April 2015). "Social Anxiety and Response to Touch: A Preliminary Exploration of Broader Autism Phenotype in Females". SAGE Open. 5 (2): 215824401558085. doi:10.1177/2158244015580854. hdl:2299/16551. S2CID14324454.
^Torres, Elizabeth B.; Isenhower, Robert W.; Yanovich, Polina; Rehrig, Gwendolyn; Stigler, Kimberly; Nurnberger, John; José, Jorge V. (1 October 2013). "Strategies to develop putative biomarkers to characterize the female phenotype with autism spectrum disorders". Journal of Neurophysiology. 110 (7): 1646–1662. doi:10.1152/jn.00059.2013. PMID23864377.
^Russell, Ginny; Ford, Tamsin; Steer, Colin; Golding, Jean (2010). "Identification of children with the same level of impairment as children on the autistic spectrum, and analysis of their service use". Journal of Child Psychology and Psychiatry. 51 (6): 643–651. doi:10.1111/j.1469-7610.2010.02233.x. PMID20345841.
^Dworzynski, Katharina; Ronald, Angelica; Bolton, Patrick; Happé, Francesca (1 August 2012). "How Different Are Girls and Boys Above and Below the Diagnostic Threshold for Autism Spectrum Disorders?". Journal of the American Academy of Child & Adolescent Psychiatry. 51 (8): 788–797. doi:10.1016/j.jaac.2012.05.018. PMID22840550.
^Cohen, Ira L.; Tsiouris, John A.; Flory, Michael J.; Kim, Soh-Yule; Freedland, Robert; Heaney, Glenn; Pettinger, Jill; Ted Brown, W. (May 2010). "A Large Scale Study of the Psychometric Characteristics of the IBR Modified Overt Aggression Scale: Findings and Evidence for Increased Self-Destructive Behaviors in Adult Females with Autism Spectrum Disorder". Journal of Autism and Developmental Disorders. 40 (5): 599–609. doi:10.1007/s10803-009-0908-z. PMID19941156. S2CID23789973.
^Huke, Vanessa; Turk, Jeremy; Saeidi, Saeideh; Kent, Andy; Morgan, John F. (2013). "Autism Spectrum Disorders in Eating Disorder Populations: A Systematic Review". European Eating Disorders Review. 21 (5): 345–351. doi:10.1002/erv.2244. PMID23900859.
^Mandy, William; Chilvers, Rebecca; Chowdhury, Uttom; Salter, Gemma; Seigal, Anna; Skuse, David (1 July 2012). "Sex Differences in Autism Spectrum Disorder: Evidence from a Large Sample of Children and Adolescents". Journal of Autism and Developmental Disorders. 42 (7): 1304–1313. doi:10.1007/s10803-011-1356-0. PMID21947663. S2CID18639019.
^Van Wijngaarden-Cremers, Patricia J. M.; van Eeten, Evelien; Groen, Wouter B.; Van Deurzen, Patricia A.; Oosterling, Iris J.; Van der Gaag, Rutger Jan (March 2014). "Gender and age differences in the core triad of impairments in autism spectrum disorders: a systematic review and meta-analysis". Journal of Autism and Developmental Disorders. 44 (3): 627–635. doi:10.1007/s10803-013-1913-9. PMID23989936. S2CID1705914.