Mark Daly, senior author of the study and assistant professor of medicine at Massachusetts General Hospital, said that while this abnormality does not mean a person is definitely going to develop autism, it appears to raise the risk substantially.
"As with just about every genetic mutation, not everyone who inherits the mutation gets a specific or conclusive diagnosis of autism," Daly explained. "This speaks to the fact that genetics never works in deterministic fashion -- it's a product of many genes in the genome acting simultaneously, plus external and environmental factors playing a role."
This study is not the first to draw a link between abnormalities on chromosome 16 and autism. Researchers at the University of Chicago led by Dr. Edwin Cook, associate professor of psychiatry and pediatrics, first made this association in a study published in the Dec. 21, 2007, issue of the journal Human Molecular Genetics.
"[This study] doesn't change that we already know that autism is more genetic than environmental, but it does contribute to our specific knowledge of what specific variants on what specific genes may contribute [to autism]," Cook explained. "These studies represent the incremental work necessary to explain the complex nature of the estimated 90 percent causation of autism attributed to genetics."
However, researchers for this latest study also found that this so-called "hot spot" in the human genome for spontaneous deletion and duplication on chromosome 16 is also likely to be associated with clinical manifestations beyond autism. Other disorders associated with this chromosome abnormality include mental retardation and multiple congenital abnormalities.
"New technologies that are allowing geneticists to study very small deletions and duplications in the genome are finding out that this kind of variation is the cause of some diseases and disorders," said Geraldine Dawson, chief science officer of the autism advocacy group Autism Speaks.
"Genetics will now begin to examine the genes that are located in this region of chromosome 16 … If we can isolate the specific genes in this region of chromosome 16 that [are] related to autism, this will be an important step toward understanding the biological basis of the disorder, which is necessary for developing medical treatments."