Boys are almost five times more likely than girls to be diagnosed with autism spectrum disorder (ASD). Many diseases are more prevalent in one sex over another but a new study suggests autism may not be one of them. The study finds that symptoms of autism in girls are so different than boys’ symptoms that girls are often misdiagnosed or their diagnosis comes much later than most boys’ diagnoses.

The reasons why gender differences exist remains unknown at this time, according to Dr. Paul Lipkin, who led the study. Lipkin is director of the Interactive Autism Network (IAN) at the Kennedy Krieger Institute, a division of the Johns Hopkins University School of Medicine in Baltimore, Maryland. The IAN is described in Lipkin’s study as a “US web-based family-powered registry for ASD.”

Lipkin questioned whether these differences are the result of biology, society, diagnosis, or the ASD screening process itself. The scope of his study was to detect and identify gender differences but the findings suggest the need for further study to determine cause.

The findings of Lipkin’s study were presented recently at the annual meeting of the Pediatric Academic Societies, held in San Diego. For the study, Lipkin’s research team reviewed registry data collected between November 2006 and January 2013 which involved 15,644 children younger than 18. The age of first diagnosis was available for 9,932 of the children as were the scores of the Social Responsiveness Scale (SRS) for 5,103 children.

Some gender differences the researchers identified include:

• Girls were diagnosed for pervasive developmental disorder, on average, at age 4.
• Boys were diagnosed at approximately 3.8 years of age.
• Girls were diagnosed with Asperger’s syndrome around age 7.6 years.
• Boys were diagnosed at 7.1 years.
• Girls with ASD tend to have greater difficulty reading social cues than boys.
• Boys have more mannerism-related issues, such as repetitive behaviors, than girls.
• Between ages 10 and 15, boys are more likely to have trouble communicating in social settings than girls will.

Lipkin describes the typical boy’s ASD symptoms as more apparent than the subtle social symptoms girls tend to develop, a finding that makes ASD symptoms in girls difficult to recognize. “Since the problems experienced by girls are in social cognition and require social opportunities, they are much more likely to be unnoticed until the elementary school years,” said Lipkin.

According to data collected by the Centers for Disease Control and Prevention, one in 42 boys in the US were diagnosed with ASD in 2010 but the diagnosis rate in girls was 1 in 189. Other characteristics of the disease include:

• Older parental age increases the likelihood of ASD.
• Premature birth and low birth weight increase risk.
• Identical twins are more likely than fraternal twins to both be diagnosed with ASD.
• When one child in a family has ASD, siblings are at greater risk for it, too.
• About half of all children with ASD test average to above average for intellectual ability.
• ASD care in the US in 2011 topped $9 billion.

Children of all ethnic, racial, and socioeconomic groups have been diagnosed with ASD. The rate of ASD diagnosis in the US has risen 120% since 2000. It is unknown at this time if the rise is the result of more children developing the disease, greater diagnostic tools, or increased public awareness of the disorder.


Sources:

1. Lipkin, Paul H, et al. "Gender Differences in Diagnosis and Social Characteristics of Children With Autism (ASD) from a US Registry." Pediatric Academic Societies. San Diego, CA. 28 Apr. 2015. Web. 6 May 2015.
2. "Autism Spectrum Disorder (ASD): Data & Statistics." CDC / Centers for Disease Control and Prevention. US Department of Health & Human Services, 26 Feb. 2015. Web. 6 May 2015.