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Psychology Professor Provides Clues about Autism Causality through Birth Order Study

by University Relations

More children are diagnosed with autism each year than juvenile diabetes, AIDS, and cancer combined. According to the Centers for Disease Control, autism now affects 1 in 88 American children, prompting researchers to scramble for answers. Hoping to provide a significant piece to this complex puzzle, Loren Martin, Ph.D., APU professor and director of research for the Department of Graduate Psychology, published the results of his groundbreaking study linking birth order to autism severity in the November 30, 2012, issue of PLOS ONE, a leading peer-reviewed scientific journal.

Martin’s study, representing the largest analysis of birth order and birth interval effects on autism to date, involved more than 300 sibling pairs diagnosed with Autism Spectrum Disorder (ASD) from the Autism Genetic Resource Exchange database utilizing information collected over the past 10 years. Using the Social Responsiveness Scale (SRS), a validated measure of autism severity, Martin discovered that overall symptoms are more severe in the second-born child with autism than in the firstborn. The study also revealed that this difference in autism severity across birth order is only observed when the birth interval is less than two years.

“Autism is diagnosed 10 times more frequently today than it was in the early 1990s, now affecting greater than one percent of the population,” said Martin. “While this rise partially correlates to an increase in awareness and broadened diagnostic criteria, the role of environmental factors cannot be ruled out.”

Based on this premise, Martin’s study of families with multiple affected children may provide clues about the causes of ASD. “The findings 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.” Additionally, his study reports that female siblings diagnosed with ASD experienced more severe symptoms than males. These results are consistent with a recent study demonstrating that autism is underdiagnosed in girls unless they have intellectual or behavioral problems associated with their ASD. Martin’s study also confirms previous reports indicating IQ decreases between first- and second-born children with autism.

Martin’s findings pave the way for a range of studies that can contribute to the discovery of autism’s underlying etiology. “Of course, the ultimate goal is to find treatments or a cure for autism, and only more research can get us closer to that,” he said. “Each new study provides clues to the cause of autism.” The search for the cause mobilized the U.S. government and research organizations to invest more than $1 billion in autism studies over the past decade as researchers seek answers to this crisis, but this investment in research pales in comparison to the $137 billion annual cost of autism to society.

“As an internationally recognized researcher, deeply committed to APU’s God First mission, Dr. Martin is making significant advances in the field of autism research,” said Robert Welsh, Ph.D., dean of the School of Behavioral and Applied Sciences. “His exemplary research is his Christian vocation. Dr. Martin’s high-quality work bolsters the academic reputation of the university and has the potential to impact the lives of millions.”

Martin first became interested in the biological underpinnings of autism when, as an undergraduate student at Olivet Nazarene University, he provided behavioral therapy to a child with autism. At the University of Tennessee Health Science Center, where he earned his Ph.D., he studied the role of cerebellar neuropathology in autism. Martin completed postdoctoral work at the MIND (Medical Investigation of Neurodevelopmental Disorders) Institute at the University of California, Davis. He began teaching at APU in 2006.

APU graduate Narges Horriat ’11 coauthored the autism study. Preliminary research for the study involved several former APU students: Tori Pike ’08, BSN ’10; Kristin Shier ’08, M.A. ’11; Bethany Vaudrey ’09, M.A. ’12; Brittany Benson ’09, and Megan Shelby ’09.

For more information or to support this effort, email Martin at lamartin@apu.edu.

Originally published in the Spring '13 issue of APU Life. Download the full issue (PDF).