Summary: A study using MRI scans found significant sex-specific brain development differences in children with autism aged 2-13, with girls showing a thicker cortex at age 3 and faster cortical thinning by middle childhood.
Key Takeaways:
- Sex-Specific Brain Differences: A UC Davis study found significant differences in brain development between autistic boys and girls aged 2-13, with autistic girls showing a thicker cortex at age 3 and faster cortical thinning by middle childhood.
- MRI Utilization: The study, part of the MIND Institute’s Autism Phenome Project and GAIN study, used MRI scans of 290 autistic and 139 non-autistic children to reveal these sex-specific brain changes.
- Underdiagnosis of Females: The findings address the underdiagnosis of autism in females, suggesting that biological differences, not just diagnostic biases, contribute to the disparity in autism diagnosis rates between males and females.
- Need for Inclusive Research: The study underscores the importance of including both sexes in autism research to understand the full spectrum of brain development differences, calling for more focus on autistic girls, who make up about 20% of the autistic population.
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A UC Davis study, published in Molecular Psychiatry, reveals significant brain development differences between autistic boys and girls aged 2-13. Led by Christine Wu Nordahl, PhD, a professor in the Department of Psychiatry and Behavioral Sciences at UC Davis, the research highlights sex-specific changes in cortical thickness. At age 3, autistic girls have a thicker cortex compared to non-autistic girls, while these differences are less pronounced in autistic boys. By middle childhood, autistic girls show faster cortical thinning than boys, indicating early and dynamic variations in brain development.
Autism Studies Highlight Sex Differences
The study is part of the MIND Institute’s Autism Phenome Project (APP) and the Girls with Autism Imaging of Neurodevelopment (GAIN) study. Utilizing MRI scans of 290 autistic and 139 non-autistic children, the researchers categorized the children by sex assigned at birth. Lead author Derek Andrews, PhD, an assistant project scientist at the MIND Institute, emphasizes the importance of including both sexes in longitudinal studies to capture the full spectrum of brain development differences. He explains that understanding how sex differences in brain development interact with autistic development is crucial for grasping the distinct developmental outcomes in boys and girls.
The findings address the underdiagnosis of autism in females, who are diagnosed with autism far less frequently than males. Nearly four males are diagnosed for every one female. Nordahl points out that while part of this sex bias is due to underdiagnosis, the study suggests that biological differences also play a role. She explains that the brain’s outer layer, the cortex, composed of millions of neurons, thickens rapidly until about age 2 and then begins to thin. Previous studies found that this thinning process differs between autistic and non-autistic children, but whether these differences were shared by autistic boys and girls had not been examined until now.
Faster Cortical Thinning in Autistic Girls
The researchers discovered that at age 3, autistic girls had a thicker cortex than non-autistic girls, with differences spanning approximately 9% of the total cortical surface. However, differences in autistic boys compared to non-autistic boys were less widespread. Additionally, autistic females showed faster rates of cortical thinning into middle childhood compared to males, with these differences present across multiple neural networks.
Andrews notes that the most surprising finding was that the differences were greatest at younger ages. By middle childhood, due to the rapid cortical thinning in autistic girls, the differences between autistic males and females became less pronounced. This highlights the necessity of studying brain development over time in both sexes to understand the full picture.
Nordahl, who now directs the APP, emphasizes that if the study had only looked at boys at age 3 or only at both sexes at age 11, they might have missed these critical sex differences. This underscores the importance of including both sexes in autism research. Nordahl launched the GAIN study in 2014 to increase the representation of autistic girls in research, addressing the disparity in the APP’s original sample, which included significantly more boys than girls.
Researchers Call for More Focus on Autistic Girls
The GAIN study is unique, and Andrews hopes other researchers will follow suit by including more autistic girls in their studies. Autistic females make up about 20% of the autistic population, and any comprehensive effort to understand autism must include them.
