For many years girls were not diagnosed as being on the autistic spectrum, not even as being high-functioning Asperger’s Syndrome. The reason most commonly given for this lack of diagnoses was that girls have better communication and social skills than boys and develop behaviors that allow them to pass as neurotypically normal.

Recently, researchers have discovered scientific reasons for perceived differences between boys and girls that help explain why girls aren’t diagnosed as being autistic as often as boys. Genetics research has identified 50 genes linked to autism and may discover more. According to Joseph Buxbaum, director of the Seaver Autism Center, believes “Autism is highly genetic, and a big part of the genetic risk is inherited.” Thus, due to having twice as many genetic mutations as boys, girls have a much higher genetic threshold to be autistic than do boys. So, to a considerably extent, girls are shielded by genetics from autism.

Earlier studies found that cells involved in the brain’s process of synaptic pruning, known as microglia, are thought to be involved in the development of autism. Recent research from the University of California finds that microglia differ in number and behavior in boys versus girls, and the genes that cause microglia to develop are more active in males, especially in the months before birth.

Studies in Australia discovered that couples with an autistic child are as much as 25 percent more likely that their next child will be autistic, and boys are at least four times more likely to develop autism than girls. Not only do more boys develop autism than girls, their symptoms are often more severe. Thus, boys are often diagnosed far earlier when they can receive better supportive services. That Tookie’s autism was never diagnosed is now more easily understood.

<Next time brain differences between normal boys and girls and those with autism>