Childhood Autism: Differences Between Boys And Girls Disappear At The First Signs

Recent studies have shown that, in the early years of life, boys and girls with autism show few or no clinically significant differences. This suggests that the differences that are noticed later in life may be influenced by external factors, such as social experiences. Detecting these similarities early is essential to improving diagnosis and gender-equal treatment.

Understanding whether there are noticeable differences between boys and girls with autism is very important. This is because, if there are such differences, health professionals can improve early diagnosis methods, learn more about the causes of autism and develop more effective treatments early on.

Observing these differences early on, especially in studies that follow children over time, can help parents and doctors better understand how autism develops differently in each sex.

However, the results of studies on these differences have been contradictory. Some studies suggest that girls with autism have better social skills, more subtle autistic behaviors, fewer repetitive behaviors and more developed language skills than boys.

Other studies claim the opposite: that girls have more social difficulties and even more intellectual disabilities than boys with autism. There is also research that indicates that there are no relevant differences between the sexes in terms of cognition, attention or behaviors linked to autism.

This lack of consensus has led scientists to propose different theories to explain why autism may appear differently in boys and girls, such as the idea that girls have some biological protection against autism, or that autism is an extreme form of certain characteristics that are more common in male brains.

Another concern is that, because of this confusion, girls with autism may end up being underdiagnosed, that is, not identified correctly, and receiving less adequate support.

Part of this problem may be less related to the biology of autism and more linked to the way studies are conducted, for example, with small sample sizes or with methods that do not analyze the data in depth.

We already know that autism begins to develop during pregnancy, even before birth. Therefore, it is essential to study children as early as possible, since very early life experiences can strongly influence a child's behavior.

For example, studies show that children who grew up in institutional settings and then moved to homes with greater cognitive stimulation could gain up to 15 IQ points.

Another study showed that children with autism showed significant improvements in language skills if they received interventions before 18 months of age. This suggests that studying infants and young children gives scientists a closer look at the onset of autism, before life experiences have such a strong influence on behavior.

However, many studies have only looked at older children or adults, which can make it difficult to separate what is biologically caused by autism from what is a result of lived experience.

Interestingly, more differences between boys and girls tend to emerge in studies of older children, which reinforces the need to investigate these differences earlier, when the condition is still developing.

Many previous studies have limitations. Most have looked at very small groups of children, typically between 28 and 96 participants, which makes it difficult to draw reliable conclusions. Few studies have focused on the earliest ages that would be ideal for understanding the origins of autism.

Many studies have used participant selection methods that are not representative of the general population, for example, by only studying children who have already been referred by clinics or only siblings of children with autism.

This can create bias, as these children may have more severe symptoms or different profiles than other children. Another problem is that some studies have used only parental reports rather than expert assessments using specific, reliable tools.

In addition, many studies have not looked at how symptoms change over time, nor have they compared children with autism to others who have developmental delays, which would make it difficult to know whether the differences seen are truly specific to autism.

And almost no studies have used modern data-clustering methods to look at different profiles of children with autism in more detail.

To try to overcome these limitations, the researchers used a project called Get SET Early, which conducts population-based screenings across San Diego County in the United States. With this project, they were able to study a very large group of 2,618 young children, 1,539 with autism and 1,079 without. Some of these children with autism were as young as 12 months old.

The method allowed boys and girls with autism to be assessed equally, without favoritism or bias, and allowed comparisons with children with developmental delay or typical development. The researchers used detailed clinical data, machine learning (a type of artificial intelligence), and even eye-tracking tests to understand how children pay attention to social stimuli.

They also followed the children over time to see how their symptoms evolved. What they found was that there were virtually no differences between boys and girls with autism on almost every measure they looked at, including symptom severity, language, and social attention.

Among typically developing children, girls performed better in several areas, such as language and social skills.

They also divided the children with autism into groups with different levels of abilities, and even then they found no major differences between the sexes. Overall, the results suggest that, in the early years of life, boys and girls with autism have very similar profiles.

This suggests that the differences that appear later on may be influenced by external factors, such as social experiences, cultural expectations, or even how boys and girls are treated or observed by adults.

This image shows how boys (blue) and girls (pink) with and without autism (ASD and TD, respectively) responded to social stimuli in scientific tests. In the left panel (a), the image shows where the children looked: children with autism (ASD) tended to focus less on the girl’s face, compared to typically developing (TD) children. The graphs below show that this difference in social attention did not vary much between boys and girls. In the right panel (b), the graphs compare performance on different tests: social affect, word production, receptive language, and visual perception. In almost all tests, girls and boys with autism performed similarly, while in the typically developing group, girls had a slight advantage. This reinforces the conclusion that, in early childhood, gender differences in autism are minimal or nonexistent.

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Large-scale examination of early-age sex differences in neurotypical toddlers and those with autism spectrum disorder or other developmental conditions

Sanaz Nazari, Sara Ramos Cabo, Srinivasa Nalabolu, Cynthia Carter Barnes, Charlene Andreason, Javad Zahiri, Ahtziry Esquivel, Steven J. Arias, Andrea Grzybowski, Michael V. Lombardo, Linda Lopez, Eric Courchesne, and Karen Pierce 

Nature Human Behaviour (2025)

https://doi.org/10.1038/s41562-025-02132-6

Abstract:

Autism spectrum disorder (ASD) is clinically heterogeneous, with ongoing debates about phenotypic differences between boys and girls. Understanding these differences, particularly at the age of first symptom onset, is critical for advancing early detection, uncovering aetiological mechanisms and improving interventions. Leveraging the Get SET Early programme, we analysed a cohort of 2,618 toddlers (mean age: ~27 months) through cross-sectional, longitudinal and clustering analyses, performed using statistical and machine learning approaches, to assess sex differences in groups with ASD, developmental delay and typical development across standardized and experimental measures, including eye tracking. The results revealed no significant sex differences in toddlers with ASD across 17 of 18 measures, including symptom severity based on the Autism Diagnostic Observation Schedule, receptive and expressive language based on the Mullen Scales of Early Learning and social attention based on the GeoPref eye-tracking test. In contrast, girls with typical development outperformed boys on several measures. Subtyping analyses stratifying toddlers into low, medium and high clusters similarly showed virtually no sex differences in ASD. Overall, our findings suggest that phenotypic sex differences are minimal or non-existent in those with ASD at the time of first symptom onset.