13 Feb


For years, it has been widelyseen that more boys than girls are diagnosed with autism (typically a female:male ratio of 1:4) and that identification of the diagnosis occurs at a later age in girls than boys. In addition, a general observation is that girls diagnosed at later ages have more symptoms than boys of the same age, including lower IQ scores. The reasons for these gender differences remain to be understood. Below are some explanations suggested in prior research.

1. Genetic Factors

Genetic mutations linked to autism are more frequently found in girls than boys. Since this appears to be a contrarian explanation to why the prevalence of autism is lower in girls, a related question is – is there a protective effect carried amongst those genetic mutations.
Further studies, such as one conducted in unaffected siblings of girls with autism, suggested that more genetic mutations are required for the autism diagnosis to become manifest in girls. This would imply a greater vulnerability to the autism gene factors in males, a gender difference also apparent in ADHD. Researchers have thought that detecting and understanding that "protective effect" seen in girls could open the door to preventing or reducing the appearance of the debilitating symptoms of autism.

2. Brain structure

Researchers took a standard set of MRI images of each participant in a sample of men and women with and without autism to see if there were any perceptible differences in brain activity between the men and women. There was.

The MRI scans revealed that the brain anatomies of females with autism were substantially different when compared to males with autism; notably, the differences were in entirely different regions of the brain. After technical analysis, the researchers concluded that females with autism showed neuroanatomical masculinization, that is, their brain structures looked more like the brain structures of the males in the non-autistic group.

3. Differences in the prevalence of core symptom criteria

Girls are more able to identify emotions in others. Research that compared the ability of girls and boys in a population that exhibited autistic traits found that girls were better able than boys to recognize emotions in photos showing facial expressions. Since lack of social recognition and empathy is a typical sign of autism, better ability of girls with autism contributed to the slow detection of the autism diagnosis.

In finer analysis, gender differences were found when the diagnostic groups were classified according to how each individual met the ASD criteria – fully (meeting all ASD criteria) or partially (meeting some but not all ASD criteira). In the full ASD subtype, males exhibited more social and communication difficulties; females showed more problems with the repetitive behaviors. In the partial criteria group, females exhibited fewer social and communication difficulties. In general, regardless of filling full or partial ASD criteria, females showed more problems than boys with regard to the trend toward repetitive behaviors.These sub-type differences, which conform to the observed variability of symptom expression and intensity in autism, should be taken in consideration when developing educational and treatment directions for persons with autism.

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