Tuesday, December 20, 2005

New Autism Spectrum Disorder research

New research with rats suggests that oxygen deprivation during birth could be a contributing cause of autism. There's no easy way to test the oxygen-deprivation theory in humans, and the finding isn't likely to lead to better treatments in the near future. Still, the research gives scientists greater insight into how factors other than genetics may play a role in autism, said Fabrizio Strata, a neuroscience researcher at the University of California, San Francisco and co-author of the study. Symptoms of autism, the most common condition in a group of developmental disorders known as autism spectrum disorders, can range from mild to severe. The disability usually strikes by age 3. It lasts a lifetime, and there is no cure, although some people with autism can learn to function well. According to the U.S. Centers for Disease Control and Prevention, autism is characterized by three distinctive behaviors. Autistic children have difficulties with social interaction, display problems with verbal and nonverbal communication, and exhibit repetitive behaviors or narrow, obsessive interests. Scientists are not certain what causes autism, but it is likely that both genetics and environment play a role. For reasons that aren't clear, autism seems to have become more common in recent years. One hotly debated theory suggests that vaccines are responsible, although some studies have failed to find a link. Oxygen deprivation during birth is considered one possible cause because it can lead to brain damage. By boosting the level of nitrogen in the air, Strata and colleagues deprived rat pups of normal levels of oxygen for as long as 10 to 12 minutes during birth. When the rats grew older, they displayed symptoms similar to those found in autistic children. It took longer for the rats to respond to some sounds, for example, and the brain regions that handle sound were disrupted. Why would a baby be oxygen-deprived in the first place? According to Strata, a complicated labor can cut off a newborn's oxygen supply, as can a twisted umbilical cord. Andy Shih, chief science officer with the National Alliance for Autism Research, said the oxygen-deprivation study presents an "interesting hypothesis," although the research hasn't been confirmed in humans. It's possible that future research could lead to changes in obstetric practices to minimize the chance that babies will go without oxygen, Shih said. But "we're far away from that at this point." The study findings appear in the Dec. 19-24 issue of the Proceedings of the National Academy of Sciences.