Towards sex- and gender-informed autism research

There is a burgeoning interest, among autistic people and their families, clinicians, researchers and the general public, in the characteristics and experiences of girls and women on the autism spectrum. To a large extent, this has been driven by a growing awareness that autistic females are under-recognised (Loomes et al., 2017). They are more likely than equivalent males to be diagnosed late, or not at all (Dworzynski et al., 2012; Russell et al., 2011). As a result, they are at greater risk of missing out on the understanding and support that can stem from an autism diagnosis. To address this inequity, a subdiscipline of autism research has sprung up, aimed at elucidating the nature of sex and gender differences on the autism spectrum, and how these impact the life chances of autistic girls and women (Lai et al., 2015). This Special Issue of Autism, which includes studies from 10 countries across 4 continents, was designed to showcase the exciting range of work within this subdiscipline, with a particular emphasis on work of direct clinical relevance. It is designed to point towards the future, by presenting studies that have taken fresh approaches to elucidating the moderating roles of sex and gender on the autism spectrum. Duvekot et al. (2017) offer important new insights into the nature of the diagnostic bias against females. They screened for autism in children presenting to general child and adolescent mental health services, using the Social Responsiveness Scale, Second Edition (SRS-2), and then conducted a thorough autism assessment with those who screened positive. Among the screen-positive children, the male-to-female ratio was 2.6:1, whereas among those who, after comprehensive assessment, received a full autism diagnosis it was higher, at 3.7:1. One interpretation of this finding is that females with high levels of autistic difficulties, as measured by the SRS-2, are less likely than equivalent males to meet autism diagnostic criteria clinically even if they undergo an autism assessment that meets current standards for best practice. This could arise from a nosological problem, whereby our current conceptualisation of autism fails to encompass important female-typical manifestations of autism. Furthermore, there may also be a diagnostic challenge to the timely recognition of autism in females, for example, contemporary assessment methods may lack sensitivity to parts of the female autism phenotype (Lai et al., 2015). These challenges may explain why in current diagnostic practice, girls and women often need to present with more concurrent behavioural, developmental or mental health issues for an autism diagnosis would be made, compared to their male counterparts (Duvekot et al., 2017; Dworzynski et al., 2012). Several studies in this Special Issue help us better understand what is driving the under-recognition of autism in females. Frazier and Hardan (2017) employed sophisticated psychometric analytic techniques, including those based on item response theory, to investigate the nature of sex/gender differences on standardised measures of autism symptomatology. They provide the most conclusive evidence to date that compared to autistic boys, autistic girls score lower on measures of focused restricted interests. Most importantly, they found evidence supporting measurement equivalence and similar symptom structure on the Autism Diagnostic Interview–Revised (ADI-R) and SRS items across males and females; Grove et al. (2017) show similar findings on the Autism Spectrum Quotient–Short Form. Together, these studies provide the first empirical evidence which reported that sex/gender differences in autism characteristics are due to true differences in the mean levels of the construct being assessed, rather than a result of different constructs being measured. This measured mean-level difference may directly impact diagnosis, as Duvekot et al. (2017) found that repetitive and stereotyped behaviour (RSB), including restricted interests, was a better indicator of autism diagnosis in boys than in girls. The finding that on average, autistic females score lower on measures of RSB than do autistic males raises a question crucial to the study of sex and gender differences in autism, namely, whether current instruments adequately capture all manifestations of autism in females. After all, all autism measures were designed and validated using predominantly male samples. Both Frazier and Hardan (2017) and Duvekot et al. (2017) raise the possibility that current measures may not be capturing female-typical RSBs and suggest that these may be expressed differently in girls and women. The idea that there are important qualitative sex/gender differences in RSB and beyond is supported by other studies in this Special Issue. Halladay et al. (2017) report the first study to examine clinicians’ perspectives on male–female differences in autism characteristics. They found that Towards sexand gender-informed autism research 706904 AUT0010.1177/1362361317706904AutismEditorial editorial2017