Sex differences have been found amongst toddlers and young children with autism spectrum disorder (ASD). We investigated the presence and stability of these ASD sex differences throughout childhood and adolescence. Participants (N = 325, 52 females; aged 3-18 years) consecutively received an ASD diagnosis at a clinic for assessing high-functioning ASD (mean verbal IQ = 92.6). There were no IQ sex differences. By parent report and direct observation, females had less repetitive stereotyped behaviour (RSB), with male-equivalent levels of social and communication impairment. Teachers reported males with ASD as having greater externalising and social problems than females. The female phenotype we describe was stable across our sample's age range. Their milder RSBs and less severe difficulties at school may lead to under-recognition of ASD in females.

Autism is more commonly diagnosed in males than females. One explanation is the 'female protective effect': there is something inherent in being female which reduces the likelihood of developing autism. However, evidence suggests that the condition is underdiagnosed in females, perhaps because females express their autism in ways which do not meet current diagnostic criteria. This review explores evidence for a female-typical autism presentation, the Female Autism Phenotype (FAP) and the component of camouflaging (compensating for and masking autistic characteristics) in particular. The evidence so far supports the existence of a female-typical autism presentation, although further examination of the characteristics and their impact across all genders and ages is needed.

BackgroundAutistic traits are widely distributed in the general population, but the boundaries of the autistic spectrum are unclear. Whole-population surveys of unselected samples of children are hampered by the lack of appropriate screening instruments.AimsTo assess whether the Social and Communication Disorders Checklist (SCDC) fulfils the need for a sensitive measure of autistic traits, which can be completed in a few minutes and which measures heritable characteristics in both males and females.MethodA 12-item scale, the SCDC, was completed by three independent samples drawn from a twin register, a group with Turner syndrome and children with a diagnosis of autistic-spectrum disorder attending clinics. The data were used to establish the heritability reliability and validity of the checklist.ResultsTraits measured by the SCDC were highly heritable in both genders (0.74). Internal consistency was excellent (0.93) and test–retest reliability high (0.81). Discriminant validity between pervasive developmental disorder and other clinical groups was good, discrimination from non-clinical samples was better; sensitivity (0.90), specificity (0.69).ConclusionsThe SCDC is a unique and efficient first-level screening questionnaire for autistic traits.

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Highlights• Current approaches to measuring camouflaging appear to measure two distinct but potentially related elements of camouflaging, namely, 'camouflaging intent' and 'camouflaging efficacy'.• Adults with more self-reported autistic traits report greater engagement in camouflaging.• Sex and gender differences exist in camouflaging.• Higher self-reported camouflaging is associated with worse mental health outcomes.• Study designs are limited by poor participant characterisation and representativeness.