Girls with autism tend to be diagnosed later than boys, largely because they can present with different characteristics than those classically related to autism, according to new research from Flinders University.

This under-detection could be partly driven by differences in the way girls typically present compared to boys. In addition, clinicians have a restricted conceptualisation of how autism can be expressed, often using tools designed around a male presentation.

“Tools currently being used to measure ASD (autism spectrum disorder) traits are based on research from male participants, meaning that they are not sensitive to how girls present,” Flinders University lead researcher Dr Joanna Tsirgiotis said.

The research demonstrated that autistic females may have less obviously unusual intense interests and fewer repetitive behaviours and are often highly socially motivated and eager for friendships, unlike what is often assumed about children with autism. Females often had better imaginative and social mimicry skills which may allow them to copy the behaviours of others and camouflage their difficulties, resulting in diagnosis being overlooked. “This is important because without a diagnosis, they are more likely to not receive the support they may need,” she said.

The researchers analysed profiles of 777 children using two commonly used diagnostic tools measuring ASD traits. It found that differences between boys and girls identified in this study, both in symptom type and severity, may render the female presentation of ASD less recognisable to referrers, such as parents, teachers and clinicians tasked with assessment.

“Girls tend to engage in less obviously neurodivergent behaviour and this can add murkiness to the diagnostic picture. If we don’t have a clear idea of ASD in girls, their characteristics can be misinterpreted as anxiety, quirkiness or even as ‘normal’ behaviour. If the female presentation is less recognisable, ASD diagnosis may be delayed or overlooked entirely.”

In another study, researchers looked at clinical judgement and decision making and found that diagnosticians may be much less confident in autism assessment for girls and interpreted ASD behaviours differently depending on the child’s sex.

Diagnosticians find it harder to assess girls because their difficulties are often more subtle in social environments, and they lack trust in our current assessment tools and criteria which are less than ideal in reflecting girls’ experience of ASD, Tsirgiotis said.

The researchers suggested that timely ASD diagnosis requires greater understanding of the unique challenges faced by autistic girls, and that assessing practitioners are made aware of more subtle or alternate expressions of neurodiversity, adapting their assessment to what is being learnt about autism in girls.

The research, ‘Sex/Gender Differences in CARS2 and GARS-3 Item Scores: Evidence of Phenotypic Differences Between Males and Females with ASD’ was published in the Journal of Autism and Developmental Disorders.