Assistant Professor Clare Harrop  Hi, my name’s Clare Harrop,   and I’m an Assistant Professor at  the University of North Carolina,   at Chapel Hill. My programme of research for many  years has focused on autistic females, from early   in development through to adulthood. The goal of  this Explainer Learn is to provide an overview of   the current state of play for autistic females.  I’m going to cover sex differences in diagnosis   of autism, the factors that influence delayed or  misdiagnosis, and the current state of research. In this Explainer, I will mostly focus on sex  differences. That is the assigned sex one is   given at birth. I will also touch on gender,  as this is really important in autism, and   influences how males and females are perceived and  socialised in the world. But, for the most part,   I will be talking about males and females,  based on how they were assigned at birth. So, first, it is well known that females are  diagnosed with autism at a lower rate to males.   This finding has been well-established over many,  many years of research, and has held relatively   constant, until recently. The first descriptions  of autism described autism as “a variant of male   intelligence.” Original case reports of autism  were all from males, as such females were rarely   diagnosed with autism. As this view started to  change, the ratio of males and females diagnosed   with autism remained high. For many years, females  were only diagnosed if they had complex support   needs, often, co-occurring intellectual  disabilities, or profound language delays. This male view of autism has certainly continued  to cloud Clinician and Teacher views of autism.   Boys are still more likely to be referred for an  autism evaluation, and one study reported that   Clinicians are hesitant, or less confident,  in giving an autism diagnosis to females.   Parents in another study discussed their child  needing to look “more impaired,” and there is   a general sense that females have to tick  more boxes to receive an autism diagnosis. For many years, the ratio of males to  females sat around four-to-one. However,   recent estimates have slowly begun to reduce,  with the most recent Center for Disease Control   estimates in the US reporting 3.6  males to one female. As a result,   interest in autistic females has  steadily started to increase. Another consistent finding is that autistic  females are diagnosed later than males. Data   from both the US and Europe suggest that females  are diagnosed 12 to 18 months later than males,   and this is often despite very few differences  in parent-reported milestones. A later age of   diagnosis is particularly true for females without  a language delay, potentially suggesting that   autism is harder to diagnose when females  present with language in the typical range. Autistic females are also more likely  to be considered late diagnosed,   receiving their diagnosis later in  childhood, or even in adolescence   and adulthood. Females are more likely to be  misdiagnosed, often experiencing diagnostic   overshadowing. This is when a previous  diagnosis, or a co-occurring diagnosis,   overshadows a Clinician’s judgement, and they  are less open to giving an autism diagnosis,   explaining challenges and differences  through existing diagnoses – diagnosis. It is important to note that with misdiagnosis  and delayed diagnosis comes later support for   autistic females, or supports that may not  be appropriate. We currently know very little   about intervention for autistic females, with  only a handful of studies addressing this. But   this is an area of great importance,  given the fact that autistic females   often have poorer outcomes in adulthood,  such as employment and mental health. A recent review by Estrin and colleagues  identified factors that serve as potential   barriers for diagnosis in females. These included  compensatory behaviours that females use,   parental concerns, perceptions of others, lack  of information surrounding autism in females,   and Clinician bias. They also cited  perceived gendered characteristics,   that may influence how people view autism in  females. These include behavioural problems,   language, relationships, co-occurring diagnoses,  and restrictive and repetitive behaviours. In line with this review, there is increasing  evidence that autism may present differently   in females, and at different stages across  their lifespan. It is possible that these   subtle and nuanced differences contribute  to delayed and misdiagnosis, as autism for   many years was conceptualised  from a largely male viewpoint. Prior to diagnosis, early in development,  we see very few differences between males   and females. This data is mostly based  on retrospective parent report. Parents   of females later diagnosed with autism  report earlier first phrases and words,   and the initial concerns of parents vary  between males and females, with more language   delays reported for males and motor delays for  females, which are not a core area of autism. When focused on children with a diagnosis, females  have been found to differ most consistently from   males in the area of restricted and  repetitive behaviours. Restricted and   repetitive behaviours are defined as,  “restricted behaviours or interests,   repetitive body mannerisms, or insisting  on doing things in a specific way.” They   are a core characteristic of autism and their  presence is required for a diagnosis. Their   play also appears more gender typical,  more elaborate and playing with toys   we typically associate with females. This  may contribute to females being overlooked. In childhood and adolescence, girls often  have fewer hand and finger mannerisms,   and less repetitive object use. However, they  may demonstrate more instances of things such   as hair pulling, or certain sensory behaviours  and responses. The interests of females have   also been more commonly reported to  fall along traditional gender lines,   such as an interest in dolls, or  hobbies more commonly seen in girls.   This goes against our traditional  male view of interests in autism. Challenges and social communication  interactions are also a core diagnostic   feature of autism. Again, research has  highlighted the subtle ways autistic   males and females differ in their use  of language and social relat – and their   social relationships. Autistic females  are described as more socially motivated,   they report closer friendships than males,  they play more closely with peers. They are   more likely to use gestures than males, have  more complex and flowing conversational skills,   and spend more time looking at faces when  methods such as eye tracking are used. It is important to note that the differences that  we describe between males and females may reflect   camouflaging or masking. Camouflaging refers  to using compensatory strategies to mitigate   day-to-day challenges. This is not unique to  autism, but it occurs at higher rates in autism,   particularly in females. So, many of these  strengths could be learnt behaviours that   girls have developed over time, and  could have negative downstream effects,   such as delaying diagnosis and putting  extreme pressure on an individual. As autistic females grow up, as with  autistic males, we see high rates of   co-occurring mental health conditions, such  as anxiety and depression. Autistic females   are also at an increased risk for eating  disorders, sleeping problems, and suicidal   ideation. Females also experience more social  isolation in adolescence and adulthood. This   is thought to reflect the changing nature of  female friendships from elementary school,   with female relationships based more on  sharing and trust. Females in adulthood   also have difficulty retaining employment, and  may experience sexual vulnerability. Female sex   thus may be a protective factor in some areas,  but a vulnerability factor for other areas. In a recent paper, Lai and colleagues  provided clear examples of how autism   presentations may be modulated by sex,  and how Clinicians, and also caregivers,   may spot these subtle differences. For  example, the DSM-5 criteria for social,   emotional reciprocity, females may engage  in back and forth conversations, but these   may appear superficial. Conversations may be  more flowing when talking about interests that   are particularly interesting for females. In line  with this, focused interest may be more gendered,   or what we consider neurotypical, based on our  historic male view of autism. They may also be   more social in nature, again, highlighting nuanced  and subtle differences between males and females. To conclude, as we learn more about the female  autism phenotype, these differences between   males and females may contribute to delayed or  underdiagnosis in females. There is still so much   we need to learn about autistic females, such  as their developmental trajectories, how being   autistic and female impacts key developmental  transitions, such as puberty and the transition   to adulthood, and what supports autistic female’s  need to thrive, and how these may vary from males. As the gap between males and females  narrows, from four-to-one in 2016,   to 3.6-to-one in 2020, our research  and clinical practices must consider   the female autism phenotype, as well  as gendered expectations for females,   that may contribute to their under  recognition and phenotypic presentation.