An Azusa Pacific University professor has linked autism to various factors including birth order, IQ and gender.
According to Loren Martin, professor and director of research for the Department of Graduate Psychology at APU, autism severity increases between first and second born affected siblings, and is more likely when births occur within two years of each other.
The study, published in the Nov. 30 issue of leading peer-reviewed scientific journal PLOS One, is the first time a link between birth order and the severity of autism symptoms is established.
The study also confirms reports indicting that IQ decreases between the older affected sibling and the second sibling.
Female siblings were also more severely impacted by autism symptoms than males, according to the study.
The 10-year research involved more than 300 sibling pairs diagnosed with an Autism Spectrum Disorder, or ASD.
“Autism diagnoses are over 10 times more common today than they were the 1990s, with 1 in 88 children affected,” said Martin, who holds a Ph.D. from the University of Tennessee Health Science Center. “While this rise is at least partially related to an increase in awareness and broadened diagnostic criteria, the role of environmental factors cannot be ruled out. The study of families with multiple affected children can provide clues about the causes of ASD. The findings from this study suggest a dosage-type effect in some cases of ASD in which genetic and/or environmental factors accumulate across pregnancies leading to a more severe manifestation of ASD symptoms.”
UCLA researchers recently published findings that air pollution in the L.A. basin may be linked to autism.