Autism is a devastating disorder, one made even more painful for families who say their child seemed perfectly normal in the first year of life, only to lose speech and other social skills as a toddler. Many scientists doubted those reports, saying parents may have not noticed early signs of trouble.
Those children really did regress, according to researchers at the University of Washington who watched home video of children's first and second birthday parties. Children whose parents reported problems early on used complex babbling, pointing, and words less often at 12 months than normal children, and less often than children whose parents say they later regressed.
Not only did the children who regressed not seem to be having problems, they actually used complex babbling, words, and declarative pointing more often than typically developing infants. But by their second birthday parties, those children were using words, pointing, and gazing socially less frequently.
"It is heartbreaking when a child who was developing normally loses their ability to talk and relate to others and develops autism," says Geraldine Dawson, a professor of psychology at the university who led the study, published in the August Archives of General Psychiatry.
"In typical babies, the period between 12 and 24 months is marked by dramatic gains in both social and language development. In toddlers with autism, this appears to be a period in which the condition actually worsens. Ideally, we will someday be able to detect young infants at risk for autism before this period and possibly prevent this decline from occurring."
Scientists are still trying to figure out how autism develops early in life, and Dawson's findings support the current sense that there are many different causes for the neurodevelopmental disorder, with regression perhaps a distinct subtype.
Other researchers have been looking for genes that cause autism, since the disorder clearly runs in families. But the hunt for a single autism gene has come to naught, and scientists now think that at least 10, and maybe as many as 100, genes could be involved, influencing each other in subtle yet devastating ways.
Duke University Medical Center researchers say they've found two autism-related genesgenes that control brain receptors for GABA, a chemical that acts as a "slow down" signal in the brain. Those genes were prime suspects because GABA plays a role in early brain development, and some people with autism have abnormal GABA levels. By looking at genes in 470 families with autistic members, the Duke team identified one GABA receptor gene they think is in involved in the origin of autism, and a second that they think interacts with the first to increase autism risk.
A damaged GABA system could flood the brain with sensory information, leading to some autistic behaviors, the researchers say. Their work is published online in the September American Journal of Human Genetics.